Physics Forums | Science Articles, Homework Help, DiscussionJoin the world's largest and highest quality physics community. Find experts discussing the latest physics research. Students can request homework help for all sciences. We offer STEM career and academic counseling.Thu, 20 Sep 2018 14:51:35 +0000Thu, 20 Sep 2018 14:51:35 +0000Physics Forums | Science Articles, Homework Help, Discussion
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Hi GuysThu, 20 Sep 2018 14:48:47 +0000
https://www.physicsforums.com/threads/hi-guys.955775/
https://www.physicsforums.com/threads/hi-guys.955775/invalid@example.com (Sisko)Sisko Hi Guys]]>1Photonic ICsThu, 20 Sep 2018 14:47:33 +0000
https://www.physicsforums.com/threads/photonic-ics.955787/
https://www.physicsforums.com/threads/photonic-ics.955787/invalid@example.com (MUBARAK ALI)MUBARAK ALI1Vector additionThu, 20 Sep 2018 14:47:12 +0000
https://www.physicsforums.com/threads/vector-addition.955811/
https://www.physicsforums.com/threads/vector-addition.955811/invalid@example.com (Jeremy Mercier)Jeremy Mercier1. The problem statement, all variables and given/known data
A man walks 120m [S 23 E] Then turns and walks 60m [S 10 N] solve for the displacement
2. Relevant equation:
Cosine law
3. The attempt at a solution
Solution attempt is attached as a photo, I think I might have...
Vector addition]]>1Hi all!Thu, 20 Sep 2018 14:45:23 +0000
https://www.physicsforums.com/threads/hi-all.955800/
https://www.physicsforums.com/threads/hi-all.955800/invalid@example.com (LucaNuke)LucaNuke1Quantum theory - Nature Paper 18 SeptThu, 20 Sep 2018 14:45:02 +0000
https://www.physicsforums.com/threads/quantum-theory-nature-paper-18-sept.955748/
https://www.physicsforums.com/threads/quantum-theory-nature-paper-18-sept.955748/invalid@example.com (StevieTNZ)StevieTNZhttps://phys.org/news/2018-09-errors-quantum-world.html -- which is about an open for all article in Nature Communications -- https://www.nature.com/articles/s41467-018-05739-8
Quantum theory - Nature Paper 18 Sept]]>7Random Thoughts part 6Thu, 20 Sep 2018 14:29:35 +0000
https://www.physicsforums.com/threads/random-thoughts-part-6.875108/
https://www.physicsforums.com/threads/random-thoughts-part-6.875108/invalid@example.com (Evo)Evo
Here is the last page of part 5.
https://www.physicsforums.com/threads/random-thoughts-part-5.851969/page-134]]>4311Getting Bored of my Engineering jobThu, 20 Sep 2018 14:27:29 +0000
https://www.physicsforums.com/threads/getting-bored-of-my-engineering-job.955805/
https://www.physicsforums.com/threads/getting-bored-of-my-engineering-job.955805/invalid@example.com (KL Rider)KL Rider
Anyway, I'm a mechanical engineer with 2 years of work experience and have just recently moved to a new company. And just like in my previous job, fatigue seems to be kicking in.
The job is basically a mountain of documentation,...
Getting Bored of my Engineering job]]>2Heisenberg's uncertainty principleThu, 20 Sep 2018 14:25:49 +0000
https://www.physicsforums.com/threads/heisenbergs-uncertainty-principle.955809/
https://www.physicsforums.com/threads/heisenbergs-uncertainty-principle.955809/invalid@example.com (DannyTr)DannyTr
It would be possible to extend out to an arbitrary number of follow-on measurements thereby measuring...
Heisenberg's uncertainty principle]]>Is field theory needed in Regge-theory?Thu, 20 Sep 2018 14:24:20 +0000
https://www.physicsforums.com/threads/is-field-theory-needed-in-regge-theory.955107/
https://www.physicsforums.com/threads/is-field-theory-needed-in-regge-theory.955107/invalid@example.com (Anashim)Anashim Is field theory needed in Regge-theory?]]>8Why do Harmonics Decay Faster than the Fundamental?Thu, 20 Sep 2018 14:19:40 +0000
https://www.physicsforums.com/threads/why-do-harmonics-decay-faster-than-the-fundamental.955731/
https://www.physicsforums.com/threads/why-do-harmonics-decay-faster-than-the-fundamental.955731/invalid@example.com (Joella Kait)Joella Kait16Questions Regarding a Semester ProjectThu, 20 Sep 2018 14:18:35 +0000
https://www.physicsforums.com/threads/questions-regarding-a-semester-project.955799/
https://www.physicsforums.com/threads/questions-regarding-a-semester-project.955799/invalid@example.com (sams)sams
1. What subjects should I choose? Should they be related to the topics that are...
Questions Regarding a Semester Project]]>1Question about computing residues after substitutionThu, 20 Sep 2018 14:13:01 +0000
https://www.physicsforums.com/threads/question-about-computing-residues-after-substitution.955647/
https://www.physicsforums.com/threads/question-about-computing-residues-after-substitution.955647/invalid@example.com (Belgium 12)Belgium 12
See attacged PDF file for my question
Thank you]]>2Query in Zeidler's Volume II QFTThu, 20 Sep 2018 13:53:30 +0000
https://www.physicsforums.com/threads/query-in-zeidlers-volume-ii-qft.955742/
https://www.physicsforums.com/threads/query-in-zeidlers-volume-ii-qft.955742/invalid@example.com (Avogadro Number)Avogadro Number
I am studying Zeidler's QFT Volume II, and I have a query on page 808:
It is claimed that S Ψ^+_{p,s} = (sk)Ψ^+_{p,s} when p=p^3 k.
I tried my hand at deriving this, but when we write S=S^1i+S^2j+S^3k,
then the...
Query in Zeidler's Volume II QFT]]>5Would this experiment disprove Bohmian mechanics?Thu, 20 Sep 2018 13:46:56 +0000
https://www.physicsforums.com/threads/would-this-experiment-disprove-bohmian-mechanics.954541/
https://www.physicsforums.com/threads/would-this-experiment-disprove-bohmian-mechanics.954541/invalid@example.com (john taylor)john taylor Would this experiment disprove Bohmian mechanics?]]>117Simultaneous Diagonalization for Two Self-Adjoint OperatorsThu, 20 Sep 2018 13:40:33 +0000
https://www.physicsforums.com/threads/simultaneous-diagonalization-for-two-self-adjoint-operators.955427/
https://www.physicsforums.com/threads/simultaneous-diagonalization-for-two-self-adjoint-operators.955427/invalid@example.com (LarryC)LarryCView attachment 230734
(a) and (b) are fairly traditional, but I have trouble understanding the phrasing of (c). What makes the infinite dimensionality in (c) different from (a) and (b)?]]>4Polarizing filter not vanishing the wave although 90 degreeThu, 20 Sep 2018 13:39:33 +0000
https://www.physicsforums.com/threads/polarizing-filter-not-vanishing-the-wave-although-90-degree.955779/
https://www.physicsforums.com/threads/polarizing-filter-not-vanishing-the-wave-although-90-degree.955779/invalid@example.com (Felipe Lincoln)Felipe Lincoln Polarizing filter not vanishing the wave although 90 degree]]>4Question about MultimetersThu, 20 Sep 2018 13:31:31 +0000
https://www.physicsforums.com/threads/question-about-multimeters.955765/
https://www.physicsforums.com/threads/question-about-multimeters.955765/invalid@example.com (AchillesWrathfulLove)AchillesWrathfulLove9Is a topopolis' orbit unstable?Thu, 20 Sep 2018 13:19:43 +0000
https://www.physicsforums.com/threads/is-a-topopolis-orbit-unstable.955357/
https://www.physicsforums.com/threads/is-a-topopolis-orbit-unstable.955357/invalid@example.com (Bizmuth)Bizmuth Ringworld was declared to be unstable because it rotates fast enough to create artificial gravity on the inner surface (never mind the structural material issues) and is therefore not technically in orbit around the central star.
So I've been reading up on the...
Is a topopolis' orbit unstable?]]>7Can a particle transform into its counter anti-particle?Thu, 20 Sep 2018 13:18:43 +0000
https://www.physicsforums.com/threads/can-a-particle-transform-into-its-counter-anti-particle.955732/
https://www.physicsforums.com/threads/can-a-particle-transform-into-its-counter-anti-particle.955732/invalid@example.com (MathematicalPhysicist)MathematicalPhysicist
##Electron \leftrightarrow Positron##
##Proton \leftrightarrow anti-Proton##]]>11On natural selection ...Thu, 20 Sep 2018 13:17:39 +0000
https://www.physicsforums.com/threads/on-natural-selection.955009/
https://www.physicsforums.com/threads/on-natural-selection.955009/invalid@example.com (EngWiPy)EngWiPy On natural selection ...]]>20Is the least count constant for Vernier scale or variables?Thu, 20 Sep 2018 13:14:55 +0000
https://www.physicsforums.com/threads/is-the-least-count-constant-for-vernier-scale-or-variables.955736/
https://www.physicsforums.com/threads/is-the-least-count-constant-for-vernier-scale-or-variables.955736/invalid@example.com (Medicalboy)Medicalboy1. The problem statement, all variables and given/known data
Is the least count constant for Vernier scale like 0.1 mm or variables?
2. The attempt at a solution
If the main scale readings are 10 mm and the vernier scale readings are 9 mm, the least count is MSD/VSD = 9/10 = 0.9...
Is the least count constant for Vernier scale or variables?]]>3Converting Piece-wise function to Heaviside functionThu, 20 Sep 2018 13:11:42 +0000
https://www.physicsforums.com/threads/converting-piece-wise-function-to-heaviside-function.955781/
https://www.physicsforums.com/threads/converting-piece-wise-function-to-heaviside-function.955781/invalid@example.com (Coderhk)Coderhk1. The problem statement, all variables and given/known data
Use the Heaviside function as an on the switch over the interval [a,b]. 2. Relevant equations
Let the H(x) be the Heaviside function defined as a piece-wise function such that it is zero if x is less than zero, and 1 if...
Converting Piece-wise function to Heaviside function]]>2Hiring managers say lying about your degree could cost you your jobThu, 20 Sep 2018 13:09:44 +0000
https://www.physicsforums.com/threads/hiring-managers-say-lying-about-your-degree-could-cost-you-your-job.955308/
https://www.physicsforums.com/threads/hiring-managers-say-lying-about-your-degree-could-cost-you-your-job.955308/invalid@example.com (Evo)Evo
Hiring managers say lying about your degree could cost you your job]]>13Surge ProtectorThu, 20 Sep 2018 13:01:12 +0000
https://www.physicsforums.com/threads/surge-protector.955697/
https://www.physicsforums.com/threads/surge-protector.955697/invalid@example.com (kiki_danc)kiki_danc
I have a power supply model Mean Well RS-50-24
It quotes : "Withstand 300VAC surge input up to 5 second"...
Surge Protector]]>20Decay length of the evanescent waveThu, 20 Sep 2018 12:52:28 +0000
https://www.physicsforums.com/threads/decay-length-of-the-evanescent-wave.955806/
https://www.physicsforums.com/threads/decay-length-of-the-evanescent-wave.955806/invalid@example.com (says)says1. The problem statement, all variables and given/known data
A beam of light of vacuum wavelength λ = 550nm passes from water (refractive index 1.33) into air (refractive index 1.00).
(a) What is the critical angle?
(b) Suppose the beam is totally internally reflected. At what angle of...
Decay length of the evanescent wave]]>Mathematical relationship of a thermocoupleThu, 20 Sep 2018 12:51:09 +0000
https://www.physicsforums.com/threads/mathematical-relationship-of-a-thermocouple.878367/
https://www.physicsforums.com/threads/mathematical-relationship-of-a-thermocouple.878367/invalid@example.com (CNC101)CNC1011. The problem statement, all variables and given/known data
The graph shows the response of a bare thermocouple
which has been subjected to a step change in temperature from 50°C to
10°C. Assuming that the bare thermocouple behaves as a single transfer
lag system, determine the...
Mathematical relationship of a thermocouple]]>24Simulation theoryThu, 20 Sep 2018 12:46:45 +0000
https://www.physicsforums.com/threads/simulation-theory.955774/
https://www.physicsforums.com/threads/simulation-theory.955774/invalid@example.com (Sisko)Sisko
Ever since Elon Musk brought it up, I’ve been thinking about the simulation theory (I know it’s not his original idea, it’s just the event that brought it to my...
Simulation theory]]>6How to evaluate path integrals numerically?Thu, 20 Sep 2018 12:36:33 +0000
https://www.physicsforums.com/threads/how-to-evaluate-path-integrals-numerically.954572/
https://www.physicsforums.com/threads/how-to-evaluate-path-integrals-numerically.954572/invalid@example.com (howl)howl12Finding the speed's dependence on angle θThu, 20 Sep 2018 12:34:19 +0000
https://www.physicsforums.com/threads/finding-the-speeds-dependence-on-angle-th.955735/
https://www.physicsforums.com/threads/finding-the-speeds-dependence-on-angle-th.955735/invalid@example.com (Rain10399)Rain103991. The problem statement, all variables and given/known data
Find v(θ), the dependence of the speed of the object on the angle θ. The string is ideal and there's no friction.
Finding the speed's dependence on angle θ]]>12[Solved] Evaluation of a certain complex functionThu, 20 Sep 2018 12:25:52 +0000
https://www.physicsforums.com/threads/solved-evaluation-of-a-certain-complex-function.955791/
https://www.physicsforums.com/threads/solved-evaluation-of-a-certain-complex-function.955791/invalid@example.com (maistral)maistral
What I did is simply substitute values for A and b and I noticed that it ALWAYS results to a real number. If possible, I would like to obtain the "non imaginary" function that is...
[Solved] Evaluation of a certain complex function]]>1Defining which cyclist profits the most from slipstreamThu, 20 Sep 2018 12:18:44 +0000
https://www.physicsforums.com/threads/defining-which-cyclist-profits-the-most-from-slipstream.954731/
https://www.physicsforums.com/threads/defining-which-cyclist-profits-the-most-from-slipstream.954731/invalid@example.com (Physicsterian)Physicsterian1. The problem statement, all variables and given/known data
- Question: Which cyclist (A, B or C) profits the most from cyclist slipstream (also called “aerodynamic drafting”)?
- Given: the direction of the wind, the positions of each cyclist; an illustration representing...
Defining which cyclist profits the most from slipstream]]>85Finding Time and Vf: Car chase problemThu, 20 Sep 2018 12:14:41 +0000
https://www.physicsforums.com/threads/finding-time-and-vf-car-chase-problem.955778/
https://www.physicsforums.com/threads/finding-time-and-vf-car-chase-problem.955778/invalid@example.com (Benny98)Benny98Here's the problem I was given:
Kyle is driving at a constant 45.0 m/s when he passes his street racer friend, Cameron. After a 4.00 second delay to get the car started and into gear, Cameron starts chasing Kyle with a constant acceleration of 2.00 m/s/s. How far will Cameron have to...
Finding Time and Vf: Car chase problem]]>2Comparison of high-level computer programming languagesThu, 20 Sep 2018 12:07:58 +0000
https://www.physicsforums.com/threads/comparison-of-high-level-computer-programming-languages.912188/
https://www.physicsforums.com/threads/comparison-of-high-level-computer-programming-languages.912188/invalid@example.com (hilbert2)hilbert2
Would it be useful to make a study of the computational effectiveness of equivalent codes written with Matlab, Mathematica, R Code, Julia, Python, etc. in a set of typical computational engineering problems like...
Comparison of high-level computer programming languages]]>56Hardy's approach to quantum gravity and QM interpretationThu, 20 Sep 2018 12:03:31 +0000
https://www.physicsforums.com/threads/hardys-approach-to-quantum-gravity-and-qm-interpretation.955277/
https://www.physicsforums.com/threads/hardys-approach-to-quantum-gravity-and-qm-interpretation.955277/invalid@example.com (kith)kithreformulation of QM in terms of five...
Hardy's approach to quantum gravity and QM interpretation]]>29Help with Geometric Dimensioning and Tolerancing...Thu, 20 Sep 2018 12:02:56 +0000
https://www.physicsforums.com/threads/help-with-geometric-dimensioning-and-tolerancing.955776/
https://www.physicsforums.com/threads/help-with-geometric-dimensioning-and-tolerancing.955776/invalid@example.com (Doc)Doc
I am trying to teach myself GD&T from a textbook (Fundamentals of Geometric Dimensioning and Tolerancing - Krulikowski) and would like some feedback on a drawing I've created, please see attached.
Any help/criticism would be greatly appreciated.
Regards,
Doc]]>5Bad Use of BrainThu, 20 Sep 2018 12:00:48 +0000
https://www.physicsforums.com/threads/bad-use-of-brain.955728/
https://www.physicsforums.com/threads/bad-use-of-brain.955728/invalid@example.com (BillTre)BillTreView attachment 230879]]>18My App Knows Where I'm Going and Tells Everyone TooThu, 20 Sep 2018 11:57:38 +0000
https://www.physicsforums.com/threads/my-app-knows-where-im-going-and-tells-everyone-too.955136/
https://www.physicsforums.com/threads/my-app-knows-where-im-going-and-tells-everyone-too.955136/invalid@example.com (jedishrfu)jedishrfu https://guardianapp.com/ios-app-location-report-sep2018.html]]>11Shape of SpacetimeThu, 20 Sep 2018 11:57:07 +0000
https://www.physicsforums.com/threads/shape-of-spacetime.955686/
https://www.physicsforums.com/threads/shape-of-spacetime.955686/invalid@example.com (NoahsArk)NoahsArk Shape of Spacetime]]>16Does invariance of proper time lead to the Lorentz transformation, or vice versa?Thu, 20 Sep 2018 11:51:00 +0000
https://www.physicsforums.com/threads/does-invariance-of-proper-time-lead-to-the-lorentz-transformation-or-vice-versa.955789/
https://www.physicsforums.com/threads/does-invariance-of-proper-time-lead-to-the-lorentz-transformation-or-vice-versa.955789/invalid@example.com (idea2000)idea2000 Does invariance of proper time lead to the Lorentz transformation, or vice versa?]]>4Geometric transformationThu, 20 Sep 2018 11:24:21 +0000
https://www.physicsforums.com/threads/geometric-transformation.955378/
https://www.physicsforums.com/threads/geometric-transformation.955378/invalid@example.com (Robin04)Robin041. The problem statement, all variables and given/known data
Let's call the axis of the ##z## complex plain ##x## and ##y##, so a general point can be written as ##z=x+iy##. Reflect the points of the complex plain so that the mirror line of the transformation is a line parallel to the...
Geometric transformation]]>23Resonance between spring and pendulum: Different frequenciesThu, 20 Sep 2018 11:19:07 +0000
https://www.physicsforums.com/threads/resonance-between-spring-and-pendulum-different-frequencies.955643/
https://www.physicsforums.com/threads/resonance-between-spring-and-pendulum-different-frequencies.955643/invalid@example.com (greypilgrim)greypilgrim
I have a spring with spring constant 30 N/m and a mass of 0.5 kg. With the mass at the bottom, the spring has the length 58 cm at rest. If I now pull down the mass and release it, it starts with a vertical oscillation, then the spring also starts to swing sideways like a pendulum and the...
Resonance between spring and pendulum: Different frequencies]]>1On Heisenberg's uncertainty principleThu, 20 Sep 2018 11:17:13 +0000
https://www.physicsforums.com/threads/on-heisenbergs-uncertainty-principle.955798/
https://www.physicsforums.com/threads/on-heisenbergs-uncertainty-principle.955798/invalid@example.com (Ssnow)Ssnow
## \sigma_{x}\sigma_{p} \geq \frac{\hbar}{2},##
where ##x,p## are the usual quantum operators and ##\hbar## the Planck constant divided by ##2\pi##. If I understood correctly, Gaussian states that are solution...
On Heisenberg's uncertainty principle]]>2Question regarding the Many-Worlds FormulationThu, 20 Sep 2018 11:03:14 +0000
https://www.physicsforums.com/threads/question-regarding-the-many-worlds-formulation.955486/
https://www.physicsforums.com/threads/question-regarding-the-many-worlds-formulation.955486/invalid@example.com (timmdeeg)timmdeeghere
Question regarding the Many-Worlds Formulation]]>17Mech Eng vs Physics (Material Science)Thu, 20 Sep 2018 10:59:51 +0000
https://www.physicsforums.com/threads/mech-eng-vs-physics-material-science.955801/
https://www.physicsforums.com/threads/mech-eng-vs-physics-material-science.955801/invalid@example.com (stechkin)stechkin
Quick background: I'm 26, in Australia, and have a degree in an unrelated field (economics). I'd like to go back to uni next year to study engineering or physics and I'm currently doing an enabling course since I didn't do any of the higher math/physics/chem subjects in high school....
Mech Eng vs Physics (Material Science)]]>1Why longitudinal waves are waves?Thu, 20 Sep 2018 10:46:15 +0000
https://www.physicsforums.com/threads/why-longitudinal-waves-are-waves.955196/
https://www.physicsforums.com/threads/why-longitudinal-waves-are-waves.955196/invalid@example.com (Bassel AbdulSabour)Bassel AbdulSabour23Volume and temperature rise in tissueThu, 20 Sep 2018 10:17:12 +0000
https://www.physicsforums.com/threads/volume-and-temperature-rise-in-tissue.955097/
https://www.physicsforums.com/threads/volume-and-temperature-rise-in-tissue.955097/invalid@example.com (roam)roam
The samples in my project are biological tissues which are being irradiated by a laser. In my experiment, using a thermal camera I...
Volume and temperature rise in tissue]]>22What is the physical cause behind time dilation?Thu, 20 Sep 2018 10:12:56 +0000
https://www.physicsforums.com/threads/what-is-the-physical-cause-behind-time-dilation.955558/
https://www.physicsforums.com/threads/what-is-the-physical-cause-behind-time-dilation.955558/invalid@example.com (Jazzyrohan)Jazzyrohan31Motor and BatteriesThu, 20 Sep 2018 10:09:53 +0000
https://www.physicsforums.com/threads/motor-and-batteries.955802/
https://www.physicsforums.com/threads/motor-and-batteries.955802/invalid@example.com (lekh2003)lekh2003
I'm doing a school project where we are responsible for designing a dragster race car powered by a small electric motor (1.5 to 4.5 V) h it seems to be called MOT12 (which I don't know the meaning of, it would be helpful if someone helped me understand).
We are allowed to power...
Motor and Batteries]]>1Conversion between Watt and JouleThu, 20 Sep 2018 09:40:17 +0000
https://www.physicsforums.com/threads/conversion-between-watt-and-joule.955619/
https://www.physicsforums.com/threads/conversion-between-watt-and-joule.955619/invalid@example.com (jamiebean)jamiebean
E = 2734.2 joules per gram
P = 2.73 x 109 watt/gram
q: How can this conversion work?????
E = 21000 joules per gram
P = ?]]>7Weight vs distance liftedThu, 20 Sep 2018 09:29:35 +0000
https://www.physicsforums.com/threads/weight-vs-distance-lifted.955786/
https://www.physicsforums.com/threads/weight-vs-distance-lifted.955786/invalid@example.com (cwhubb)cwhubb Weight vs distance lifted]]>1Further S matrix clarificationsThu, 20 Sep 2018 08:46:09 +0000
https://www.physicsforums.com/threads/further-s-matrix-clarifications.955660/
https://www.physicsforums.com/threads/further-s-matrix-clarifications.955660/invalid@example.com (Silviu)Silviu Further S matrix clarifications]]>3Magnet system efficiency made from neodymium magnetsThu, 20 Sep 2018 08:19:31 +0000
https://www.physicsforums.com/threads/magnet-system-efficiency-made-from-neodymium-magnets.955718/
https://www.physicsforums.com/threads/magnet-system-efficiency-made-from-neodymium-magnets.955718/invalid@example.com (Engren93)Engren93
We want to try neodymium magnets for our separator. We learned that magnetic flux density could be reached...
Magnet system efficiency made from neodymium magnets]]>2The formulae for kinetic energy and JoulesThu, 20 Sep 2018 08:16:50 +0000
https://www.physicsforums.com/threads/the-formulae-for-kinetic-energy-and-joules.955616/
https://www.physicsforums.com/threads/the-formulae-for-kinetic-energy-and-joules.955616/invalid@example.com (jamiebean)jamiebean
The formula for joules is kg x v^2
I dont understand why does the difference exist
and what is the difference between joules and kinetic energy
isnt joule the unit for energy??
Thank you guys for helping me.]]>9Conservation of angular momentumThu, 20 Sep 2018 08:10:39 +0000
https://www.physicsforums.com/threads/conservation-of-angular-momentum.955797/
https://www.physicsforums.com/threads/conservation-of-angular-momentum.955797/invalid@example.com (Mohammeddev)Mohammeddev1. The problem statement, all variables and given/known data
A rod of length D sits at rest on a friction less table. A ball of mass M strikes the end of the rod with a speed V and rebounds with a speed 3v/4 causing the rod to rotate counterclockwise around a fixed axis at one end. The...
Conservation of angular momentum]]>2Nuclear and Atomic energy levelsThu, 20 Sep 2018 08:09:04 +0000
https://www.physicsforums.com/threads/nuclear-and-atomic-energy-levels.955296/
https://www.physicsforums.com/threads/nuclear-and-atomic-energy-levels.955296/invalid@example.com (QuarkDecay)QuarkDecay
Am I missing something here? Or...
Nuclear and Atomic energy levels]]>3Sallen & Key filterThu, 20 Sep 2018 08:00:37 +0000
https://www.physicsforums.com/threads/sallen-key-filter.955700/
https://www.physicsforums.com/threads/sallen-key-filter.955700/invalid@example.com (Ravrage)Ravrage1. The problem statement, all variables and given/known data View attachment 230866
I worked out the Bandwidth at: 1500Hz so therefore Fh should be 4050Hz and Fl should be 2550Hz...
Sallen & Key filter]]>4A Question about Unit Vectors of Cylindrical CoordinatesThu, 20 Sep 2018 07:15:28 +0000
https://www.physicsforums.com/threads/a-question-about-unit-vectors-of-cylindrical-coordinates.955792/
https://www.physicsforums.com/threads/a-question-about-unit-vectors-of-cylindrical-coordinates.955792/invalid@example.com (sams)sams A Question about Unit Vectors of Cylindrical Coordinates]]>2Min max: optimal quantity of medicineThu, 20 Sep 2018 07:09:54 +0000
https://www.physicsforums.com/threads/min-max-optimal-quantity-of-medicine.955737/
https://www.physicsforums.com/threads/min-max-optimal-quantity-of-medicine.955737/invalid@example.com (Karol)Karol1. The problem statement, all variables and given/known data View attachment 230882
2. Relevant equations
Minimum/Maximum occurs when the first derivative=0
3. The attempt at a solution
$$R'=2D\left( \frac{C}{2}-\frac{D}{3} \right)-\frac{1}{3}D^2$$...
Min max: optimal quantity of medicine]]>5vector multiplication and divisionThu, 20 Sep 2018 07:09:45 +0000
https://www.physicsforums.com/threads/vector-multiplication-and-division.955795/
https://www.physicsforums.com/threads/vector-multiplication-and-division.955795/invalid@example.com (jamiebean)jamiebean2Composition of FunctionsThu, 20 Sep 2018 06:32:36 +0000
https://www.physicsforums.com/threads/composition-of-functions.955790/
https://www.physicsforums.com/threads/composition-of-functions.955790/invalid@example.com (Jpyhsics)Jpyhsics1. The problem statement, all variables and given/known data
f(x)= x/(1+x)
What is f(f(x)) and what is its domain.
2. The attempt at a solution
I found f(f(x))= x/(1+2x)
and the domain: (-∞,-1/2)∪(-1/2,∞) , but it is saying that I have the wrong domain. What mistake have I made?...
Composition of Functions]]>2What is the total torque of that system?Thu, 20 Sep 2018 06:24:40 +0000
https://www.physicsforums.com/threads/what-is-the-total-torque-of-that-system.955626/
https://www.physicsforums.com/threads/what-is-the-total-torque-of-that-system.955626/invalid@example.com (Sameh soliman)Sameh soliman1. The problem statement, all variables and given/known data View attachment 230824
A load was put on the right side of a seesaw 0.6 meter from its center as shown, on the other side a force of 49N is applied perpendicular to the seesaw surface 1 meter from its center, the setup is...
What is the total torque of that system?]]>21Simple Vector Addition ProblemThu, 20 Sep 2018 06:24:34 +0000
https://www.physicsforums.com/threads/simple-vector-addition-problem.955785/
https://www.physicsforums.com/threads/simple-vector-addition-problem.955785/invalid@example.com (ComputerForests000)ComputerForests0001. The problem statement, all variables and given/known data
"A bird flew 40 m to the west, then 100 m in a direction 36.9 degrees to the north of east. Use the algebraic addition of vectors to fins the magnitude of the bird's net displacement"
Use sin (36.9) =0.6 and cos (36.9) =...
Simple Vector Addition Problem]]>2hash marks on minkowski diagramThu, 20 Sep 2018 06:03:24 +0000
https://www.physicsforums.com/threads/hash-marks-on-minkowski-diagram.955784/
https://www.physicsforums.com/threads/hash-marks-on-minkowski-diagram.955784/invalid@example.com (idea2000)idea2000 hash marks on minkowski diagram]]>5Why does Mars have so much iron on it's surface.Thu, 20 Sep 2018 05:47:35 +0000
https://www.physicsforums.com/threads/why-does-mars-have-so-much-iron-on-its-surface.955695/
https://www.physicsforums.com/threads/why-does-mars-have-so-much-iron-on-its-surface.955695/invalid@example.com (rootone)rootone
Same is likely for Mars, but there is a lot more iron (and compounds) on the surface of Mars than there is on Earth.
Are there substantial amounts of silicate rocks, as Earth has?]]>4Is the ground state energy of a quantum field actually zero?Thu, 20 Sep 2018 05:39:20 +0000
https://www.physicsforums.com/threads/is-the-ground-state-energy-of-a-quantum-field-actually-zero.953766/
https://www.physicsforums.com/threads/is-the-ground-state-energy-of-a-quantum-field-actually-zero.953766/invalid@example.com (jcap)jcap
The simplest relativistic field theory is described by the Klein-Gordon equation of motion for a scalar field ##\large \phi(\vec{x},t)##:
$$\large \frac{\partial^2\phi}{\partial t^2}-\nabla^2\phi+m^2\phi=0.$$
We...
Is the ground state energy of a quantum field actually zero?]]>94A Question about the LagrangianThu, 20 Sep 2018 05:38:55 +0000
https://www.physicsforums.com/threads/a-question-about-the-lagrangian.954412/
https://www.physicsforums.com/threads/a-question-about-the-lagrangian.954412/invalid@example.com (sams)sams
$$L = T - U $$
And why L = T - U ?
Any help is much appreciated. Thank you.]]>6Find the Y component of Electric field at a pointThu, 20 Sep 2018 05:18:59 +0000
https://www.physicsforums.com/threads/find-the-y-component-of-electric-field-at-a-point.955747/
https://www.physicsforums.com/threads/find-the-y-component-of-electric-field-at-a-point.955747/invalid@example.com (isukatphysics69)isukatphysics691. The problem statement, all variables and given/known data
The figure below shows a thin, vertical rod of length L with total charge Q. The indicated point P is a horizontal distance x from the one end of the rod. What is the electric field at point P. Express your answer in component...
Find the Y component of Electric field at a point]]>29Cesium 137 Half-Life vs. Chernobyl ContaminationThu, 20 Sep 2018 05:09:39 +0000
https://www.physicsforums.com/threads/cesium-137-half-life-vs-chernobyl-contamination.955290/
https://www.physicsforums.com/threads/cesium-137-half-life-vs-chernobyl-contamination.955290/invalid@example.com (Mackenzie Cobb)Mackenzie Cobb
But lately, I've become...
Cesium 137 Half-Life vs. Chernobyl Contamination]]>12No metastable type IIB de Sitter vacuaThu, 20 Sep 2018 05:02:40 +0000
https://www.physicsforums.com/threads/no-metastable-type-iib-de-sitter-vacua.950271/
https://www.physicsforums.com/threads/no-metastable-type-iib-de-sitter-vacua.950271/invalid@example.com (Urs Schreiber)Urs SchreiberObied-Ooguri-Spodyneiko-Vafa 18.
Curious situation: After it had influenced much the development of the string theory community’s attention and almost all of its public...
No metastable type IIB de Sitter vacua]]>70Inertial loads -- Sources of information neededThu, 20 Sep 2018 04:56:57 +0000
https://www.physicsforums.com/threads/inertial-loads-sources-of-information-needed.955783/
https://www.physicsforums.com/threads/inertial-loads-sources-of-information-needed.955783/invalid@example.com (giovanna Centenaro)giovanna CentenaroThe Rise of Incentivized Competitions for HumanityThu, 20 Sep 2018 04:50:17 +0000
https://www.physicsforums.com/threads/the-rise-of-incentivized-competitions-for-humanity.955587/
https://www.physicsforums.com/threads/the-rise-of-incentivized-competitions-for-humanity.955587/invalid@example.com (jedishrfu)jedishrfu
The largest and arguably most influential one has been the XPRIZE organization which finds sponsors and...
The Rise of Incentivized Competitions for Humanity]]>9Problems with Raman SpectroscopyThu, 20 Sep 2018 04:34:21 +0000
https://www.physicsforums.com/threads/problems-with-raman-spectroscopy.955636/
https://www.physicsforums.com/threads/problems-with-raman-spectroscopy.955636/invalid@example.com (GuiHn)GuiHn
Recently I had a problem in the analysis of a raw material called Propranolol HCl, when performing Raman identification for the specific batch the obtained spectrum does not generate signal and, consequently, identity of the material.
By testing other techniques like infrared and NMR, I...
Problems with Raman Spectroscopy]]>3Lame JokesThu, 20 Sep 2018 04:34:02 +0000
https://www.physicsforums.com/threads/lame-jokes.25301/
https://www.physicsforums.com/threads/lame-jokes.25301/invalid@example.com (quddusaliquddus)quddusaliquddus4876What is the purpose of an inductor?Thu, 20 Sep 2018 04:23:36 +0000
https://www.physicsforums.com/threads/what-is-the-purpose-of-an-inductor.955393/
https://www.physicsforums.com/threads/what-is-the-purpose-of-an-inductor.955393/invalid@example.com (AchillesWrathfulLove)AchillesWrathfulLoveIf an inductor requires a changing current to produce a voltage drop across itself Then is there any purpose to an inductor with constant current going through it? Is AC usually used with inductors since its always changing.]]>9Switching to LinuxThu, 20 Sep 2018 04:18:01 +0000
https://www.physicsforums.com/threads/switching-to-linux.946131/
https://www.physicsforums.com/threads/switching-to-linux.946131/invalid@example.com (EngWiPy)EngWiPy Switching to Linux]]>20Buck-boost converter output current limiterThu, 20 Sep 2018 04:14:07 +0000
https://www.physicsforums.com/threads/buck-boost-converter-output-current-limiter.955696/
https://www.physicsforums.com/threads/buck-boost-converter-output-current-limiter.955696/invalid@example.com (Sid55)Sid55
Does having high continuous current discharge power source at the input help it in any way ?
This buck-boost converter offers...
Buck-boost converter output current limiter]]>10Can you fire Elon Musk as CEO?Thu, 20 Sep 2018 03:59:56 +0000
https://www.physicsforums.com/threads/can-you-fire-elon-musk-as-ceo.954848/
https://www.physicsforums.com/threads/can-you-fire-elon-musk-as-ceo.954848/invalid@example.com (nsaspook)nsaspook Can you fire Elon Musk as CEO?]]>60MBTI type (Myers-Briggs Type Indicator) -- Jung Typology Personality TestThu, 20 Sep 2018 03:54:48 +0000
https://www.physicsforums.com/threads/mbti-type-myers-briggs-type-indicator-jung-typology-personality-test.925967/
https://www.physicsforums.com/threads/mbti-type-myers-briggs-type-indicator-jung-typology-personality-test.925967/invalid@example.com (Apple_Mango)Apple_Mangohttp://www.humanmetrics.com/cgi-win/jtypes2.asp
<< Mentor Note -- INTP = Introverted iNtuitive Thinking Perceiving >>]]>22Uncertainty productThu, 20 Sep 2018 03:41:34 +0000
https://www.physicsforums.com/threads/uncertainty-product.955755/
https://www.physicsforums.com/threads/uncertainty-product.955755/invalid@example.com (Sushmita)Sushmita1. The problem statement, all variables and given/known data
For the ground state of a particle moving freely in a one-dimensional box 0≤x≤L with rigid reflecting end points, the uncertainity product (Δx)(Δp) is
(A) h/2
(B) h√2
(C) >h/2
(D) h/√3
2. Relevant equations
The...
Uncertainty product]]>4Electron sprials from r_i to r_fThu, 20 Sep 2018 03:30:44 +0000
https://www.physicsforums.com/threads/electron-sprials-from-r_i-to-r_f.955777/
https://www.physicsforums.com/threads/electron-sprials-from-r_i-to-r_f.955777/invalid@example.com (doggydan42)doggydan421. The problem statement, all variables and given/known data
Find an expression for the time it takes for an electron to spiral in from an initial radius ##r_i## to a final radius ##r_f##. Write your answer in terms of ##r_i##, ##r_f##, ##m_e##, e, and c.
2. Relevant equations...
Electron sprials from r_i to r_f]]>Aerodynamics project helpThu, 20 Sep 2018 03:14:26 +0000
https://www.physicsforums.com/threads/aerodynamics-project-help.955729/
https://www.physicsforums.com/threads/aerodynamics-project-help.955729/invalid@example.com (Kart)Kart
Now, I have looked into the basic physics that goes behind airfoils and their forces. However, I am looking for an experiment idea that is somewhat higher level (maybe undergrad...
Aerodynamics project help]]>4How can light have a wavelength or change direction in SR?Thu, 20 Sep 2018 03:03:39 +0000
https://www.physicsforums.com/threads/how-can-light-have-a-wavelength-or-change-direction-in-sr.955644/
https://www.physicsforums.com/threads/how-can-light-have-a-wavelength-or-change-direction-in-sr.955644/invalid@example.com (Amaterasu21)Amaterasu21 How can light have a wavelength or change direction in SR?]]>4Show that this graph isn't differentiable at x=1Thu, 20 Sep 2018 03:03:29 +0000
https://www.physicsforums.com/threads/show-that-this-graph-isnt-differentiable-at-x-1.955758/
https://www.physicsforums.com/threads/show-that-this-graph-isnt-differentiable-at-x-1.955758/invalid@example.com (opus)opus1. The problem statement, all variables and given/known data
Sketch the graph of the following function and use the definition of the derivative to show that the function is not differentiable at x=1.
$$f(x) = \begin{cases} {-x^2+2} & \text{if } x \leq 1 \\ x & \text{if } x > 1...
Show that this graph isn't differentiable at x=1]]>22Semi major and minor axis of polarization ellipseThu, 20 Sep 2018 02:53:04 +0000
https://www.physicsforums.com/threads/semi-major-and-minor-axis-of-polarization-ellipse.926197/
https://www.physicsforums.com/threads/semi-major-and-minor-axis-of-polarization-ellipse.926197/invalid@example.com (henil)henil2H-field and MMF in a magnetic circuitThu, 20 Sep 2018 02:39:53 +0000
https://www.physicsforums.com/threads/h-field-and-mmf-in-a-magnetic-circuit.955585/
https://www.physicsforums.com/threads/h-field-and-mmf-in-a-magnetic-circuit.955585/invalid@example.com (cnh1995)cnh1995
If the 100-turn primary of a transformer is energized with 1A dc, its mmf will be 100A-T. And all the line integrals H.dl enclosing the primary coil will equal 100A. As per magnetic...
H-field and MMF in a magnetic circuit]]>25Issues With Dark MatterThu, 20 Sep 2018 02:38:44 +0000
https://www.physicsforums.com/threads/issues-with-dark-matter.952366/
https://www.physicsforums.com/threads/issues-with-dark-matter.952366/invalid@example.com (LAP3141)LAP3141
If dark matter is the predominant form of matter in the universe, why does it have no effect on solar system dynamics? The solar system is...
Issues With Dark Matter]]>11Precision and AccuracyThu, 20 Sep 2018 02:33:59 +0000
https://www.physicsforums.com/threads/precision-and-accuracy.955762/
https://www.physicsforums.com/threads/precision-and-accuracy.955762/invalid@example.com (protractor)protractor1. The problem statement, all variables and given/known data
Two different scientists measured the speed of light four times.
Scientist A
3.80*10^{8}m/s
3.32*10^{8}m/s
3.10*10^{8}m/s
3.05*10^{8}m/s
Average...
Precision and Accuracy]]>2order of integration and taking limitsThu, 20 Sep 2018 02:22:39 +0000
https://www.physicsforums.com/threads/order-of-integration-and-taking-limits.955773/
https://www.physicsforums.com/threads/order-of-integration-and-taking-limits.955773/invalid@example.com (dyn)dyn
I came across the following integral in contour integration
lim(ε→0) "integral of" exp(iaεe^{iθ}) dθ = θ
If I take the limit first then it just becomes the integral of 1 which is θ.
I have 2 questions -
If I take the limit first and then perform the integral do I always get the same...
order of integration and taking limits]]>3Throwing a ball upwardsThu, 20 Sep 2018 02:09:20 +0000
https://www.physicsforums.com/threads/throwing-a-ball-upwards.955708/
https://www.physicsforums.com/threads/throwing-a-ball-upwards.955708/invalid@example.com (robax25)robax251. The problem statement, all variables and given/known data
A child tosses a ball directly upward. Its total time in the air is T. Its maximum height is H. What is its height after it has been in the air a time T/4? Neglect air resistance. 2. Relevant...
Throwing a ball upwards]]>7Probability that X is less than a setThu, 20 Sep 2018 01:39:07 +0000
https://www.physicsforums.com/threads/probability-that-x-is-less-than-a-set.955699/
https://www.physicsforums.com/threads/probability-that-x-is-less-than-a-set.955699/invalid@example.com (showzen)showzenStatistical Inference by Casella and Berger. My question has to do with transformations.
Let ##X## be a random variable with cdf ##F_X(x)##. We want to find the cdf of ##Y=g(X)##. So we define the inverse mapping,...
Probability that X is less than a set]]>4An introduction to meThu, 20 Sep 2018 01:20:41 +0000
https://www.physicsforums.com/threads/an-introduction-to-me.955767/
https://www.physicsforums.com/threads/an-introduction-to-me.955767/invalid@example.com (Amused_1)Amused_1
I’ve come to the forum looking for advice about a few different topics - all process based - that while technically above my pay grade I have a keen interest in for the sake of making my job easier/better.
I’m a Lead...
An introduction to me]]>3how do Calculators add fractions with different denominatorsThu, 20 Sep 2018 01:18:10 +0000
https://www.physicsforums.com/threads/how-do-calculators-add-fractions-with-different-denominators.955757/
https://www.physicsforums.com/threads/how-do-calculators-add-fractions-with-different-denominators.955757/invalid@example.com (matqkks)matqkks2Force Resultant is equal to the sum of the components -- why?Thu, 20 Sep 2018 01:14:32 +0000
https://www.physicsforums.com/threads/force-resultant-is-equal-to-the-sum-of-the-components-why.955717/
https://www.physicsforums.com/threads/force-resultant-is-equal-to-the-sum-of-the-components-why.955717/invalid@example.com (Bassel AbdulSabour)Bassel AbdulSabour3Current Status of Eternal InflationThu, 20 Sep 2018 01:13:30 +0000
https://www.physicsforums.com/threads/current-status-of-eternal-inflation.955655/
https://www.physicsforums.com/threads/current-status-of-eternal-inflation.955655/invalid@example.com (ad infinitum)ad infinitum Current Status of Eternal Inflation]]>3Projectile motion problemThu, 20 Sep 2018 01:08:18 +0000
https://www.physicsforums.com/threads/projectile-motion-problem.955766/
https://www.physicsforums.com/threads/projectile-motion-problem.955766/invalid@example.com (Jpyhsics)Jpyhsics1. The problem statement, all variables and given/known data
A m=77.39 kg person on a bike is riding at v0,b=11.83 m/s. Suddenly, he sees a child running across his path! He applies the brakes that provide a deceleration of a= -4.192 m/s2. His glasses were not...
Projectile motion problem]]>2Searching for jobs in the USA, should I quit?Thu, 20 Sep 2018 00:54:01 +0000
https://www.physicsforums.com/threads/searching-for-jobs-in-the-usa-should-i-quit.955770/
https://www.physicsforums.com/threads/searching-for-jobs-in-the-usa-should-i-quit.955770/invalid@example.com (Andromeda9010)Andromeda9010
First thing I did was applying to foreign companies and universities. I applied to many countries. I don't know why, but most of the jobs I found where in the USA, even though I was trying to avoid...
Searching for jobs in the USA, should I quit?]]>Transmission Line Transposition - Conceptual QuestionThu, 20 Sep 2018 00:53:43 +0000
https://www.physicsforums.com/threads/transmission-line-transposition-conceptual-question.955733/
https://www.physicsforums.com/threads/transmission-line-transposition-conceptual-question.955733/invalid@example.com (Marcin H)Marcin H Transmission Line Transposition - Conceptual Question]]>6Calculating the relevant variables for a rotating habitatThu, 20 Sep 2018 00:29:23 +0000
https://www.physicsforums.com/threads/calculating-the-relevant-variables-for-a-rotating-habitat.955760/
https://www.physicsforums.com/threads/calculating-the-relevant-variables-for-a-rotating-habitat.955760/invalid@example.com (Bizmuth)Bizmuth
1. The problem statement, all variables and given/known data
I want to calculate the rotational period and surface velocity of a Bishop Ring with a radius of 80 km and a surface 'gravity' of 0.86 G
I should note that this isn't for homework. It's for personal interest. I'm looking for...
Calculating the relevant variables for a rotating habitat]]>2Midway Instantaneous VelocityThu, 20 Sep 2018 00:22:21 +0000
https://www.physicsforums.com/threads/midway-instantaneous-velocity.955761/
https://www.physicsforums.com/threads/midway-instantaneous-velocity.955761/invalid@example.com (fight_club_alum)fight_club_alum1. The problem statement, all variables and given/known data
The position of a particle moving along the x axis is given in centimeters by x = 9.35 + 1.03 t3, where t is in seconds. Calculate the instantaneous velocity when the particle is midway between its...
Midway Instantaneous Velocity]]>7How to calculate force needed to get tire spinningThu, 20 Sep 2018 00:20:23 +0000
https://www.physicsforums.com/threads/how-to-calculate-force-needed-to-get-tire-spinning.955756/
https://www.physicsforums.com/threads/how-to-calculate-force-needed-to-get-tire-spinning.955756/invalid@example.com (sugarray)sugarray
This is to help give an idea of stress on a transmission.
I have searched an hour hear as well as Google looking for a formula or...