What is Homework physics: Definition and 52 Discussions

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  1. S

    Electrical engineer

    I am an electrical engineer and I like to educate high school physics
  2. A

    Calculate the spring constant of oscillating mass on a spring colliding with a wall

    So I proceed as: Total time for 1 oscillation is 0.2s $$\frac{1}{\sqrt{2}}=\sqrt{2} \sin ({\omega t_1})$$ $$\sqrt{2}=\sqrt{2} \sin ({\omega t_2})$$ Therefore $$\omega t_2=\frac{\pi}{2}$$ $$\omega t_1=\frac{\pi}{6}$$ $$\omega ×2(t_1+t_2)=2×\left( \frac{\pi}{2}+\frac{\pi}{6}\right) $$ Since...
  3. Another

    Confused between the units of a constant and the units of the integral boundary conditions

    I want to integrate this function ## \int_{0.8um}^{1.8um} A e^{B/E(x)} \, dx ## But A has a unit as ## 1/cm ##. Should I change ##1/cm## to ##1/um## by multiplying ##1/10^{4}## For this function, I decided to integrate using the online numerical integral, This side . I am just curious that...
  4. BlackPhysics

    A cylinder with cross-section area A floats with its long axis vertical

    Summary: A 5.0- cm -diameter cylinder floats in water. How much work must be done to push the cylinder 11 cm deeper into the water? F =Aρgx A 5.0- cm -diameter cylinder floats in water. How much work must be done to push the cylinder 11 cm deeper into the water? F =Aρgx x being the...
  5. B

    Min Plane Height to Drop Bomb in Hollow: 335m

    A plane is flying 80km/h in horizontal direction and it has to drop a bomb into 30m wide and 30m deep hollow. What is the smallest possible height for the plane to fly above hollow if the bomb successfully hits the bottom? I made a mistake somewhere but not sure where... the correct result is...
  6. crism7

    Calculating Time of Flight & Velocity of a Ball Thrown Upwards

    Vertical components: dy = 0m ay = 9.8m/s^2 [down] t = 1.34s V1y = required V2y = 0 i first tried to find V1y dy =vi t + 1/2 a t^2 and got V1y = -6.566 then i solved for time of flight dy =vi t + 1/2 a t^2 0 = -6.566t + 4/9t^2 and for 1.34 seconds does this mean the time of flight is the...
  7. H

    How to determine the spring constant in a Lennard-Jones potential

    Hi, First of all I hope it doesn't bother if I ask too much question.I found the values of ##u1,u2## for 2 differents posistions ##(r1,r2 )## and I now have to determine the spring constant (k).I'm thinking about using$$ F= -kx $$ with ##F = -\frac{du}{dr}## then $$ U = \int -kr \cdot dr...
  8. R

    Calculating Speed on an Incline Using the Law of Conservation of Energy

    Homework Statement A ski starts from rest and slides down a 22 o incline 75m long. Coefficient of friction is 0.090. What is the skiers speed at the base of the inlcline? Use energy methods Homework Equations PE=mgh KE=mv2/2 W=Fd The Attempt at a Solution Since mass was not given I did PE=KE...
  9. A

    What is the magnetic field generated by these two particle beams?

    A uniform beam of positively charged particles is moving with a constant velocity parallel to another beam of negatively charged particles moving with the same velocity but in opposite direction separated by a distance d. Then, how should be the variation of magnetic field B along a...
  10. Miles123K

    N-oscillator system with two sides attached

    Homework Statement The system is shown in the image. In the beaded string shown in Figure 1, the interval between neighboring beads is a, and the distance from the end beads to the wall is a/2. All the beads have mass m and are constrained to move only vertically in the plane of the paper...
  11. H

    Confusion about moment of inertia

    When a question only asks for the moment of inertia (of say, a T-section), do I have to find the moment of inertia with respect to both the x and the y axis?
  12. I

    Electric Fields and Electric forces help

    Homework Statement This is the question Structure opposite comprises 5 ions each of which has lost one electron. The sides of the square formed by the 4 outer ions are of length 0.2nm Ion E is at the midpoint 1.What is the force on A due to ion A?Homework Equations I'd imagine: F= kq / r^2...
  13. Physicsterian

    Defining which cyclist profits the most from slipstream

    Homework Statement - 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 this - NOTE that I am expected to solve this question...
  14. SmugBug

    How many air molecules are there inside the tire?

    Homework Statement A car tire has a volume of 10 L and is inflated to a gauge pressure of 30 psi (207,000 Pa) at 20°C. How many air molecules are there inside the tire?Homework Equations N = PV/ kbT The Attempt at a Solution (207,000 Pa )x (0.01 m3) / (1.38 x 10^-21 x 293) =5.12 x 10^23...
  15. Manav

    Calculating Charge Of Electron (Millikan Oil Drop Experiment

    Homework Statement I was doing the Milikan Oil Drop Experiment from a simulation this site: http://scienceclub.ucoz.com/index/0-109. I tried calculating the charge of the electron but it was from the real value. Oil Density: 920 (kg/m^3) Viscosity of Air: 1.81×10−5 kg/(m*s) Distance: 0.0025 m...
  16. H

    Find the change in the Kinetic energy of an Ideal Gas

    Homework Statement Let 3/2kT be the kinetic energy of ideal gas per molecules. T the absolute temperature and N the avogadro number. Answer the following questions : 1) when the volume doubled at constant temperature. How many times the kinetic energy per molecule become greater than before...
  17. M

    Physics Lens Problem: Find Object Distance

    Homework Statement An object and its lens-produced real image are 2.4 m apart. Part A If the lens has 55-cm focal length, what are the possible values for the object distance? Express your answer using two significant figures. Homework Equations 1/s+1/s'=1/f s-s'=2.4m The Attempt at a...
  18. A

    What are the values of Rf and V2 for the given circuit?

    Homework Statement Hello, I am trying to Calculate The Resistance Rf and the value of the Voltage V2. The setup is a logarithmic Op amp connected to a differential Op amp. Both Op amps obey the Golden Rules. Attached below is my attempt at the solution and the question. Currently, I have an...
  19. Helmy

    Question about Electric Field lines (MCQ)

    *This is a question in an assignment that i have to submit. 1. Homework Statement 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...
  20. Likith D

    The solution of a problem regarding center of mass

    A rod of mass M (=4m) and length L is placed over a smooth horizontal table. One end of rod is attached with a block of mass m through a light string as shown in the figure. The pulley is friction less and light. the acceleration of com of rod at the given instant is (g = acceleration due to...
  21. S

    Two spheres of are dropped to ground while in contact.

    Two spheres of different masses are dropped to ground.They are in contact as one above the other and are of masses, let’s say m and 2m.They are dropped with velocity v - My question is if we can conserve momentum and if we can why?And how to find the final velocity of upper ball after collision...
  22. A

    How to calculate projectile off cliff when angle is below th

    Homework Statement Cliff is 50 m tall Stone thrown downwards with velocity of 12 m/s and 22 degrees below horizontal What is the time it will take to hit the ground? Homework Equations V=d/t D= Vi t + 1/2at^2The Attempt at a Solution Vx1= cos (22)(12) = +11.12620625 Vy1= sin (22) (12) =...
  23. H

    Find the formula for refraction angle?

    Homework Statement Homework Equations Snell's Law sin tetha1/v1 = sin tetha2/v2 n1 = c/v1 n1 . sin tetha 1 = n2 . sin tetha 2 The Attempt at a Solution I try to make triangle out of line PO, so that it will have correlation to tetha, since o = center, then let's say there's point C at...
  24. H

    Electrons move, causing magnetic force, find v?

    Homework Statement Homework Equations f = q.v.B.sin tetha I = q/t = v/R The Attempt at a Solution (1) q =a.b.n.v.t is it right? (2) I = q/t = abnvt/t = abnv is it right? (3)F = q.v.B is it right? (4) ? (5) ? is it right?
  25. H

    How much of the reflected sound is heard by person A?

    Homework Statement 2. Homework Equations Doppler's Equation The Attempt at a Solution (1)[/B] freqA = (v sound - vA )/(v sound - v B) . freq B *v A = 0 (static) = V/(V - v) . freq B ...Answer : (d) (2) freq A hear which is reflected sound by D first find freq D, *v D, v A = 0...
  26. H

    How Do You Solve Complex Pendulum Equations in Physics Homework?

    Homework Statement For number 3,4,5 https://s4.postimg.org/qbp3xzq65/IMG_1092.png https://s22.postimg.org/u220j60sx/IMG_1093.pngHomework Equations Centripetal force = m v^2/R T = centripetal force + w Sigma F = m.a The Attempt at a Solution Number 3. Find the v at D point using...
  27. alan

    Temperature and volume fraction of a liquid mixture

    I have known the interaction parameter of a certain liquid mixture which has the phase behaviour can be described by the lattice model. , is it possible for us to know the temperature at the critical point? Besides, if we know the temperature at the critical point, can the volume fraction of...
  28. D

    QM: The time evolution of a Gaussian wave function

    Heads up, I only recently got into quantum mechanics and don't feel like I got a solid grasp on the material yet. 1. Homework Statement Given is the wave function of a free particle in one dimension: \begin{equation} \psi(x,0) = \left( \frac{2}{\pi a^2} \right)^{1/4} e^{i k_0 x} e^{-x^2/a^2}...
  29. A

    Physics 221 Calc-based question for homework

    Homework Statement If vector d1--> is equal to 2i^-4j^+9k^ and vector d2-> is equal to 8i^-10j^+9k^, what is (d1-->+d2-->) * (d1--> X 4d2->)? Homework EquationsThe Attempt at a Solution So I added up first two vectors and then multiplied it by the cross product but I get a vector and when I...
  30. A

    How could a DC electric motor be used to power a computer?

    Homework Statement A group of students found an old DC electric motor in a box. They were looking for a small generator they could use to power their computer while they were out camping. Explain how they might do this with the motor they found. Homework EquationsThe Attempt at a Solution
  31. K

    Understanding Work and Energy: Solving a Physics Problem

    I have been stuck on this physics question: An object is sliding along a flat surface with an initial speed of 30 m/s. What must the coefficient of kinetic friction be between the object and the surface if the object slides to a stop in 10m? What would be the speed of the object after it had...
  32. Jabbar

    Electric field due to a charged rod

    Homework Statement https://gyazo.com/d502fb408d6224ffa70700cf047bad20 (link to problem: #4). [moderator edit: Image inserted for clarity] A total charge Q is distributed uniformly over rod length L. The rod is aligned on the x-axis, with one end at the origin and the other at point x=L. a)...
  33. munirah

    How to get the matrices in partial trace

    Homework Statement Good day, I want to ask the matrix that obtained from below formula and example. $$tr_A(L_{AB})=\sum_i [(\langle i|\otimes id)L_{AB}(|i\rangle\otimes id)]$$ this formula above can be represented as in matrix form below, $$tr_A(L_{AB})=...
  34. munirah

    Reduced Density operator in matrix form

    Homework Statement I already read book of Quantum Computation and Quantum Information by Nielsen and Chuang according to reduced density operator and I already understand how to do the reduced density using Dirac notation, Ket Bra.Homework Equations [/B] My problem here I want to know the...
  35. U

    A basic conservation of energy question

    The question asks: Uranium nuclei are unstable and decay by emitting a helium nucleus, which contains two protons and two neutrons. Suppose the original nucleus has 92 protons and 146 neutrons before it emits the helium nucleus, and that the helium nucleus has an knknown speed as it departs from...
  36. L

    Path of a Particle: Find & Solve Questions

    Homework Statement Homework Equations Find the path of a particle. What is the general or fundamental way to solve this type of questions ? The Attempt at a Solution I don't know where do i start. I can't able to find a relation between these vectors.
  37. L

    Time period in harmonic oscillation.

    Homework Statement Homework Equations Find Time Period. Find the error in my solution. The Attempt at a Solution Where i am wrong ?
  38. L

    Angular Momentum of the particle.

    Homework Statement Homework Equations Find Angular Momentum. How to find velocity of a particle. The Attempt at a Solution If i differentiate with `dt` both sides, I'm getting velocity y-component=velocity x-component. Then i feel helpless:cry:
  39. L

    Falling rotating sphere and displacements

    Homework Statement Homework Equations How to locate the point P and C after 0.5s from their initial position ? The Attempt at a Solution Well i don't know whether it would be correct way to start the problem i.e find the centripetal acceleration .
  40. L

    Meter Bridge: Finding Error in Resistance

    Homework Statement Homework Equations How to find error in resistance ? The Attempt at a Solution I found out the resistance without error. But What is the way to figure out an error of an instrument ?
  41. L

    Calculating Gauge Pressure on a Sphere

    Homework Statement Homework Equations What is gauge pressure ? The Attempt at a Solution How to find gauge pressure ?
  42. L

    Can I Find the Moment of Inertia with Only 8 Equal Parts in My Homework Problem?

    Homework Statement http://i.imgur.com/7ZRsVj5.png Homework Equations I can't apply correct method ! The Attempt at a Solution In bigger figure, i cut into 8 equal parts.So , total moment of inertia=8 I But it's wrong ! I know it's wrong because i can't able to find angle between any two...
  43. L

    Magnetic Field in parallel plate capacitor

    Homework Statement A parallel plate capacitor of area 60cm^2 and separation 3mm is charged initially at 90 micro coulomb. If the medium between the plates get slightly conducting and the plate loses charge initially at the rate of 2.5 *10^-8 C per sec then what is the magnetic field between the...
  44. V

    Is Angular Momentum Conserved in Circular Motion?

    Homework Statement A bob of mass m attached to an inextensible string of length l is suspended from a vertical support. The bob rotates in a horizontal circle with an angular speed ω rad/s about the vertical. About the point of suspension : (1) angular momentum changes in direction but not...
  45. normal_force

    Impulse of force correct here?

    Im sure Imma mess this up, probably because I am really tired...but I have a bullet that weights .015kg's and is moving at 285m/s, so 609.18J's as with KE. I hit a 70kg block, penetrates .3048 meters thus exerting 1998.62N's of force, which is a lot of force. .3048/285m/s so 0.00106 seconds...
  46. Giu1iano

    Need some help with two Dimensional velocity Vectors

    Mod note: Moved from a technical section, so missing the homework template. Hi, I'm struggling to understand this problem. I would normal just wait for class but I'm away traveling for work. The question is as follows. A man has a boat that can travel at 15.0 m/s relative to the water. He...
  47. D

    Relative Velocity of Ball on Moving Board

    Homework Statement A ball rolls with a velocity of 14 mm/s [W] on a board that is being pulled [E 60o N] at 20.0 mm/s. What is the velocity of the ball relative to the floor? b = ball x = board f = floor Homework Equations V_bf = V_bx + V_xf The Attempt at a Solution I tried to work through...
  48. Julian102

    How to calculate the equivalent resistance using wye delta ?

    Homework Statement https://z-1-scontent-sin1-1.xx.fbcdn.net/hphotos-xtf1/v/t34.0-12/12435980_942112312550457_1708451532_n.jpg?oh=b29a5e9b2ff96bbf0e11932d081eb25e&oe=568A9B79 [/B] We need to find the equivalent resistance along A to B ie AB Homework Equations R=(1/R1 + 1/R2+...+1/Rn)^-1 ...
  49. M

    Potential Difference between two parallel charged plates.

    How do we find out the potential difference between two equal and opposite charged (conducting) parallel plates mathematically? Let the charge on a plate be 'Q', Total area of a plate be 'A', the distance between the plates be 'd'. I need a direct mathematical solution please, I've come across...
  50. O

    How Do You Calculate the Mass of the Plane After Intercepting Luggage?

    Homework Statement A plane with an initial velocity of (225m/s ŷ + 325m/s Ẑ) intercepts a 20kg piece of luggage with initial velocity of (-75m/s ŷ - 15m/s Ẑ). After, plane is moving at speed 400 m/s. What is the mass of the plane? Homework Equations momentum y: Mplane(225m/s) + 20kg(-75 m/s) =...