Only a force directed upward can oppose a downward force.

In the case of the spinning slingshot, we see that the stone tends to go up when the angular velocity increases.

To identify the force...

The gyroscope]]>

I understand that if there are two capacitors in a circuit with a potential difference V

Every example I have seen have been...

Two like capacitors in parallel]]>

Safe removal of an external disk]]>

lim

I feel the limit does not exist. Because sin(1/x) is largely changing value as x approaches 0,(since it is an oscillating...

does xsin(1/x) exist as x approaches zero?]]>

Some physicists consider it to be synonymous with "state preparation procedure".

Others find this too restrictive, as it would exclude states not prepared in a laboratory. For example my nose is not...

What are the issues with considering state and "state preparation procedure" to be synonymous?]]>

I have started to try to...

Weinberg and Ray Transformations – Ch2 App A.]]>

So far i'm thinking that each occupant...

Home Energy Saving System]]>

How close is Earth to the closest black hole?]]>

Two imaginary spherical surfaces of radius (R) and (2R) respectively surround a positive point charge (Q) located at the center of the concentric spheres. What is the number of electric field lines (N2) going through the sphere...

Question about Electric Field lines (MCQ)]]>

[0,1] is compact because any infinite collection of open subsets that covers the set has to include the boundry points therefore there is a finite collection of these sets that also covers

(0,1) is not...

Simple question on compactness]]>

Here is the last page of part 5.

https://www.physicsforums.com/threads/random-thoughts-part-5.851969/page-134]]>

I am using an older version of Mathematica: 10.1.0.0, the student edition. I am trying to label plots within the Plot function using the command "PlotLegend ->" but when running, first I get a message that this is outdated, and when I suppress, I get a legend that does not work with the...

Labeling plots]]>

1. if the phosphor posed any risk in a school setting, and

2. if there was a way to utilize it for a physics demonstration of some kind.

I assume they threw a rock or something at the...

Phosphor screen, hazards and demonstrations?]]>

1- What is the difference between free and open source software? Do both mean the same thing?

2- Some free (open source?) software is used by companies to make big money. Aren't these conflicting things?]]>

Suppose we have the standard rectangular potential barrier in 1D, with

$$

V =

\left\{

\!

\begin{aligned}

0 & \,\text{ if } x<0, x>d\\

V_0 & \,\text{ if } x>0,x<d\\

\end{aligned}

\right.

$$

The standard approach to solve for...

(Numerical) Boundary Value Problem for Schrodinger's Equation]]>

Thanks]]>

Let ##x_1=1## and ##\displaystyle x_{n+1} = 3 x_n^2## for ##n \ge 1##.

a) Show if ##a = \lim x_n##, then ##a = 1/3## or ##a = 0##.

b) Does ##\lim x_n## actually exist?

Showing a limit of the recurrence relation]]>

Acoustics handbook]]>

Given that ##t_1 = 1## and ##\displaystyle t_{n+1} = \frac{t_n^2 + 2}{2t_n}## for ##n \ge 1##. Show that ##t_n > 0## for all ##n##.

Intuitively this is obvious....

Proving that a sequence is always positive given relation]]>

1. The problem statement, all variables and given/known data

Given the following vector field,

$$

\dfrac{2(x-1)\,dy - 2(y+1)\,dx}{(x-1)^2+(y+1)^2}

$$

how do I integrate :

The integral over the curve x^4 + y^4 = 1

x^4 +...

Difficult Vector Field Integra]]>

If the received signal level for a particular digital system is -151dBw and the receiver system effective noise temperatyre is 1500K, what is E_b/N_o for a link transmitting 2400bps?

solution says:

(Eb/N0) = –151 dBW – 10...

Find Eb/No : signal to noise ratio]]>

I wonder how soon it will be before one of these is fitted with a machine gun. What if one of these was built or stolen for use in terrorism? In a densely populated city, how long could one of these roam freely gunning people...

Anyone else a bit concerned with autonomized weapons?]]>

Input rpm 1250 with medium shock.

Can any one help me.

Or suggest me any free software where I can get gear design.]]>

Find the exact value of ##y=cos\left(arcsin \frac {5} {11} \right)##

I'm stuck at square one. I know that I must evaluate arcsin first, which will give me an...

Finding the exact value of cos(arcsin)]]>

but alas! i can't seem to find definite answer!!!

i am currently making a fountainpen nib with a carbide point.

the traditional material for fountainpen tipping is iridium + osmium alloy...

Question regarding Hardness and Wear Resistance!]]>

Density of States alternative derivation]]>

Turns out that Zoobyshoe beat me in posting about this in another thread, so he will officially be known...

Weird News Compilation]]>

I've been reading about low gravity capillary driven flows, and no authors use Reynolds number when measuring importance of inertia in capillary driven flows. Instead most use the Ohnesorge number. Can someone explain why this is?

Thanks!]]>

Bob had a box containing 9 green balls and 1 white ball. A Bob's friend removed one ball from the box without telling Bob what was its color. Now what's the probability for Bob picking up one green ball...

Probability Problem]]>

Hello, it is me again, I recently posted about a question on moments and centre of gravity with two planks both 10 Kg in mass and 2m in lengths, uniform, situated on top of each other as shown in the picture.

The question asked...

Draw a diagram showing the forces acting on a plank and find x]]>

My wife just drew this

View attachment 93241]]>

View attachment 220921

When the circuit moves creates magnetic force that moves the some charges in the wire and that is a current.

That is what i...

Find the curret flow induced by a wire]]>

If a car has an emergency breaking system that can be pulled by the driver, which will decelerate the car at a rate of -4.0m/s^2, how long does the driver have to react before it is too late. (If she enters the intersection at...

Solving for time in frusterating dynamics question]]>

From Miriam-Webster definition of a "fowl":

1

2 a

b

PF Photo Contest - Fowl Play (2/17-2/23)]]>

On the other hand, from page...

Hamiltonian in Schrödinger: necessarily total energy?]]>

But in case of Drain Voltage changing between 0V to 5V, how does it work?]]>

Think we have a 0 degree ice. we give some energy to it (by a heater) and all of it get into a 0 degree water.

How does the kinetic and potential energy of the molecules change?

In the book in which I saw this question, it...

Kinetic energy of a solid versus a liquid at the same temperature (through a phase change)]]>

I have absolutely no idea how to do this...

But, I am assuming you use Ek=1/2mv^2, though I can't figure out how to apply it

To rearrange that:...

Velocity from a catapult]]>

Only two things are infinite, the universe and human stupidity, and I'm not sure about the former.

Albert Einstein

Common sense is the collection of prejudices acquired by age eighteen.

Albert Einstein

The fear of death is the most unjustified of all fears, for there's no...

My favored scientist quotes]]>

Rainer Kaltenbaek, Robert Prevedel, Markus Aspelmeyer,Anton Zeilinger

http://arxiv.org/pdf/0809.3991.pdf

Part of the diagram is reproduced...

Beam splitter in entanglement swapping experiment]]>

Distance to sun: ~150000000km

(assumed) distance to cloud: 2km

This means that there should be a 16 metre edge around the shadow where the...

Shadow of clouds over the Sea]]>

They see some states as separable and others as entangled. For Alice the partial measurement suboperator is diag(1,1,-1,-1) and Bob is diag(1,-1,1,-1).

Martians...

Do we need Quantum Censorship]]>

Hi,

I'm just trying to derive the small-signal model of the cascode MOSFET amplifier circuit. In the lectures, we were just given the small-signal model directly. I'm trying to derive it.

I have almost the exact same thing...

Cascode Amplifier Small Signal Model]]>

Find the equivalent resistance of this circuit between points a and b

https://imgur.com/a/LWcIC

View attachment 220864

I am not sure how to...

Find the equivalent resistance of this circuit w/o Data?]]>

\begin{equation}

\langle T\psi,\phi\rangle=\langle \psi, T\phi\rangle

\end{equation}

%Self-adjoint test

syms x

a = (diff(exp(-x^2)))*exp(-2*x^2)

b = (diff(exp(-2*x^2)))*exp(-x^2)

W = int(a, x)

P = int(b, x)

O=W-P

and it is...

Making a short test for self-adjointness]]>

When reading a bit about substractive color mixing, a question came up.

View attachment 219068

I understood that when mixing Cyan, Magenta and Yellow paint, you would get black because all these 3 colors that get reflected by each corresponding paint are absorbed by the other...

Question about subtractive color mixing]]>

I am physics student close to my masters and I intend to enter finance after my PhD (Investmentbanking, Hedge- / Quantfonds, Riskmanagement).

For that, I am aware that a PhD in theoretical physics would be preferable since it will increase my programming and modelling skills.

However,...

Preparing for a job in finance/risk management]]>

Why does ENGR Mechanics: Statics cover *hinged* trusses?]]>

Science and math books with nice covers]]>

Car water pump barrier to flow when off?]]>

Linear motion question -- Drops falling from a dripping faucet]]>

Considering 2 scattering particles with momenta ##p_{1}, p_{2}##, where ##p_{2} = 0## in the Lab reference. The momenta of these 2 particles after elastic collision are ##p_{1}', p_{2}'##, respectively. Due to the 4-momentum...

Scattering angle in relativistic kinematics]]>

https://www.researchgate.net/public...l_differential_equation_based_on_Haar_wavelet

They solve equation 18 by the transform method. It is however unclear what they do from step 3 to equation 19. They solve this:

\begin{equation}...

Use of initial conditions to solve nonlinear ODEs]]>

If you have kids/will have kids, what would you want them to know by the time they enter the work force?]]>

What separates Hilbert space from other spaces?]]>

View attachment 220909

View attachment 220908

C is the point of contact and G is the CM of the plank . x be the distance between G and C .Since...

Plank oscillating on a log]]>

Equivalence of quantified statements]]>

Mass of bound particles]]>

All the data is on the sheet. I named the nodes V1 to V4, however I'm primarily evaluating in terms of V3 and V4. The x=V3 and y=V4 are for the systems solving I'm using. I've looked and looked at this problem, and seem to be...

Nodal Voltage Analysis with dependent sources]]>

I was re-reading my old Relativity book (by Rindler) and taking a look at some of the problems. He asks: Using a Minkowski diagram to establish the following result:

Given two rods of rest lengths ##l_1## and ##l_2 (l_2 <...

inertial frame where rods have same length]]>

View attachment 220881

The original question given above has been correctly answered by me .The correct option is 2) .

Thinking more about this problem...

Could this bulb resistance problem be modified ?]]>

Approach taken in the solution in the book:

Passwords with 6 characters P6 = 36^6 − 26^6 = 1,867,866,560.

Similarly, we have P7 = 36^7 − 26^7 =...

Problem on Counting - Number of Passwords]]>

Heat transfer from a closed cylinder filled with fluid]]>

I recently purchased a book on relativity called "Gravity in a Nutshell" by Zee. While it is interesting I find his conversational style to be too chatty. I prefer a little more of a "get to the point" conversational style.

I'm going to be modeling the evolution of the...

Gravity in a Nutshell too chatty, would like something else]]>

How to prove ##max\{0, \rho(\sigma)+\rho(\tau)-m\}\leq \rho(\tau\sigma)\leq min\{\rho(\tau), \rho(\sigma)\}##?

Let ##\sigma:U\rightarrow V## and ##\tau:V\rightarrow W## such that ##dimU=n##,...

Proving a statement about rank of transformations.]]>

- The global mean surface temperature is 14.46 °C computed from MODIS data (2001-2012).

- Estimated Jan 1951-Dec...

Mean Earth temperature]]>

The problem relates to the subject of torque and angular momentum:

A man of mass ## M ## stands on a railroad car that is rounding an unbanked turn of radius R at speed v.

His center of mass is height ## L ## above the car, and...

Man on a railroad car]]>

I am preparing a phosphate and a bicarbonate buffer at pH 7.4. I am not using the tradition of making a "rough" buffer and then adjusting the pH to the desired value as I want to target a certain value of osmolarity in both...

Thermodynamic vs apparent ka]]>

If 100 pounds/kg, for example, were placed point 1, what would the force be at points A, B, C and D? Would the...

Force distribution]]>

A cylinder with radius R spins around its axis with an angular speed ω. On its inner surface there lies a small block; the coefficient of friction between the block and the inner sur- face of the cylinder is μ. Find the values...

Block in a rotating cylinder]]>

I am focused on Chapter 2: Differentiation ... ...

I need help with an aspect of D&K's notation for directional and partial derivatives ... ...

D&K's definition of directional and...

Directional and Partial Derivatives ...Notation ... D&K ..]]>

So, if you consider the above cube, if we shoot a particle in a straight line such that it crosses the face ABEF and it...

Why is the Uncertainty principle inherent to particles?]]>

I am on page 22, equation (1.5.58). The authors are deriving the Hermitian conjugate of the Dirac equation (in order to construct the current). I am able...

Hermitian conjugate of the derivative of a wave function]]>

Mary and Frank are each in their own rocket ships moving along the x-axis. Mary's ship passes Frank's ship at t

Galilean Transformations Problem: Two moving Rockets+Missile]]>

http://www.latticeguy.net/mypubs/pub017.pdf

http://bose.res.in/~bossar/chandu.pdf

What I'd like to know is the following:

Without superstrings. Quark confinement and asymptotic freedom...

quark confinement and higgs mechanism]]>

I am focused on Chapter 2: Differentiation ... ...

I need help with an aspect of D&K's notation for directional derivatives ... ...

D&K's definition of directional and partial...

Directional Derivatives ... Notation ... D&K ...]]>

Wednesday, 1 pm EST. You can use the forum for time zone conversion: This post was posted 3:55 pm EST.

While the announcement doesn't have any details, digging a bit...

7 exoplanets around TRAPPIST-1]]>

My question has more or less to do with infinity based on the Planck scale, assuming the Big Bang occurred at no specific point in space-time.

Assuming the Planck particle is the smallest form...

Superposition in Open/Closed Systems]]>

A 24 kg object is placed at the top of an incline with height 500m and length 375m. The coefficient of kinetic friction is 0.600

1) Find the acceleration of the object.

2) Find the speed by the time it has reached the bottom of...

Compute acceleration on an inclined plane with frict]]>

Three non-equal positive point charges, q

I...

Three charges constrained to a ring]]>

Relative speed and time dilation]]>

In this case, four numbers , what is meaning of it?]]>

Examine the following diagram of a particle accelerator.

View attachment 220768

a) Give a brief explanation of how it works.

b) Describe what might happen to the particle accelerator if the magnetic field was too weak.

c)...

Synchrotron Accelerator]]>

Derive an equation for the velocity vx(t), vy(t) of the particle. -

Deriving equation for velocity of a particle]]>

It is spread through drinking water contaminated with human waste....

Cholera Vaccines Being Tried Out]]>

I have been wondering why train simulators(and trains themself) have a kW specification, AND a maximum force indication.

If I would calculate the speed of a train using some formula, then where is the power value used for?

Does it have something to do?

Or is only the maximum...

What does power have to do with the speed calculations of a Train?]]>

Transforming to local inertial coordinates]]>

Adiabatic or Isobaric process?]]>