Kinetic Definition and 1000 Threads

  1. P

    Momentum vs Kinetic Energy in classical physics

    I've added 'in classical physics' in the thread title because all the differences between them that I found on the internet involved relativistic physics. It was something like both momentum and kinetic energy being components of a four-momentum or something like that. But I cannot understand...
  2. Minestra

    Change in rotational kinetic energy

    Homework Statement A disk of mass m1 is rotating freely with constant angular speed ω. Another disk of mass m2 that has the same radius is gently placed on the first disk. If the surfaces in contact are rough so that there is no slipping between the disks, what is the fractional decrease in the...
  3. Wout Veltman

    I Kinetic Energy & Speed in Inertial Frames: Chris, Bob & Angelica

    From Chris' perspective Bob is traveling with 1.5*108 m/s in direction a. Angelica is also traveling with 2.4*108 m/s in direction a. From Bob's perspective Chris is traveling with 1.5*108 m/s in direction b (The opposite of x). Angelica is traveling with 1.5*108 m/s in direction a. They all...
  4. R

    How can I calculate kinetic friction?

    Homework Statement A child slides down a slide with a 28 degree incline , and at the bottom her speed is precisly half what it would have been if the slide had been frictionless. Calculate the coefficient of kinetic friction between the slide and the child. Homework Equations Newtons second...
  5. audrey1203

    How to find the coefficient of kinetic friction?

    Homework Statement A child slides down a slide with a 28° incline, and at the bottom her speed is precisely half what it would have been if the slide had been friction-less. Calculate the coefficient of kinetic friction between the slide and the child. Knowns: 28° speed=V/2 Homework Equations...
  6. C

    Where does kinetic energy go in inelastic collision?

    I'm having a bit of trouble conceptualizing this. I've looked all over the Internet, and I've been seeing that in completely inelastic collisions the reason that kinetic energy is not conserved is because energy goes into deformation, sound, propelling shrapnel, and especially heat (among other...
  7. O

    Calculate momentum, kinetic energy, speed etc. for a decay

    Homework Statement I have the decay K+ → μ+ + νμ Calculate: 1. Momentum of μ+ 2. Total energy of νμ 3. Mass of K+ 4. Speed of μ+ 5. Speed of νμ Homework Equations The only thing we get are the kinetic energy of μ+ so Kμ+ = 152.53 MeV and the mass of mμ+ = 105.658 MeV/c2 The Attempt at a...
  8. A

    Help understanding answers: kinetic friction

    https://scontent-dft4-1.xx.fbcdn.net/v/t35.0-12/14796269_10210868496286479_1115393743_o.jpg?oh=0ccd692c60a1d0bab84d5fbaf7e6197b&oe=580A1894 In the figure, a 6-kg box is sliding up an incline that makes an angle of theta=30 degree (with respect to the horizontal). As it slides up the incline, a...
  9. sa1988

    Verify that this kinetic energy operator is Hermitian

    Homework Statement Not actually a homework question but is an exercise in my lecture notes. Homework Equations I'm following this which demonstrates that the momentum operator is Hermitian: The Attempt at a Solution$$KE_{mn} = (\frac{-\hbar^2}{2m}) \int\Psi_{m}^{*} \Psi_{n}^{''} dx $$ $$...
  10. JustynSC

    What is the Force of Kinetic Friction?

    Homework Statement a 10 kg box is moving on a level floor. The coefficient of static friction between the box and floor is 0.3. What is the force of kinetic friction? Homework Equations fk = FN * μk The Attempt at a Solution I rearranged the formula so that everything was set equal to the...
  11. Clara Chung

    Kinetic energy distribution of free electrons

    Is the distribution the same as Boltzmann distribution? Have anyone made a mathematic equation for the KE of free electrons on a piece of metal?
  12. E

    Physics Homework: A bead on wire

    Homework Statement A bead slides on a wire, which is in a vertical plane, as shown in the diagram. Gravity acts in the -y direction. The bead starts at A, moving to the right with an initial velocity v. The wire is frictionless between A and D and between F and G, but there is friction between...
  13. Eclair_de_XII

    Finding coefficient of kinetic friction from thermal energy?

    Homework Statement "A rope is used to pull a ##\frac{357}{100}kg## block at constant speed ##\frac{203}{50}m## across a horizontal floor. The force on the block from the rope is ##\frac{768}{100}N## and directed ##15°## above the horizontal. What are (a) the work done by the rope's force, (b)...
  14. D

    Derive the equation for kinetic energy and gravitional energ

    Homework Statement A wooden toy mouse of mass (m) is attached to a spring with constant (k) and suspended vertically as shown below. The toy is released at the point the spring is unstretched at position x = +A, passes through equilibrium at x = 0 and the spring’s maximum extension occurs at x...
  15. B

    To stop a moving object -- Momentum or Kinetic Energy

    How should I look at the problem at stopping a moving object with the following conditions 1) mass m and speed v 2) 0.5 m and 2v 3)0.5m and sqrt 2 v Simple math tells me the number 2 would require more energy to stop it. I can relate to energy better in terms of how to stop a moving mass...
  16. E

    What percentage of the original kinetic energy is convertible?

    Homework Statement Ball 1 has an inertia of 0.500 kg and ball 2 has an inertia of 0.600 kg . Ball 1 is moving away from you at 5.0 m/s, and you decide to throw ball 2 at it to make it go faster. The balls collide head-on, and the coefficient of restitution for the collision is 0.95. Part A)How...
  17. T

    I Substituting a solid body with mass points

    I ran into the following problem, and stuck for a couple of days now. I have a solid body, rigid and and has uniform density. Its mass M, the location of the center of gravity x_M, y_M, z_M and its inertia matrix is known: Jx Jxy Jxz Jyx Jyy Jyz Jzx Jzy Jz I have to write an algorithm...
  18. G

    Is Force a Conservative Vector Field?

    1. The problem statemees and given/known data A ball has a potential energy of 200J. Once the ball reached the ground, it's kinetic energy was 175J. Is this possible and does this defy the conservation of energy? Homework Equations KE = PE The Attempt at a Solution I am not sure. Being in high...
  19. J

    Is My Calculation of Kinetic Energy Change Correct?

    Homework Statement Homework Equations ΔKE=W+FcosΘd KE=.5mv^2 Final Vel^2=initial Velocity^2+2ax The Attempt at a Solution So calculate the force at x=2.6 to -5.356N, set 2.6(-5.356)=1.3Vf^2-1.3(0^2) which seemed to prove a problem as the square of the final velocity was negative, but just...
  20. T

    Dashpots and the Work - Kinetic Energy Theorem

    Homework Statement I need to accommodate a dashpot in an intentionally simple work-kinetic energy analysis method. For example, for a box being dragged up a ramp via a rope while attached to a spring, I can deal with the work done by gravity, rope tension, spring force, and friction via the...
  21. terryds

    Static friction vs kinetic friction in Tablecloth trick

    In the tablecloth trick, if we pull the tablecloth with a great force, the objects on it will stay on the table. But, if we pull it gently, the objects on it will still get along with the cloth movement. I know that if the force exceeds the maximum value of static friction, the objects will...
  22. Green dwarf

    Is electromagnetic radiation a form of kinetic energy?

    Hi, I'm a high school science teacher. Most textbooks classify EM radiation as kinetic energy. But this doesn't seem right to me. As a photon is massless it's hard to see how it can have kinetic energy which is 1/2 mv^2. It could be said that it has energy hf and therefore mass hf/c^2. Then its...
  23. Mayan Fung

    I Exploring the Kinetic Energy Operator: Why is it Differentiated Twice?

    When I learned about operators, I learned <x> = ∫ Ψ* x Ψ dx, <p> = ∫ Ψ* (ħ/i ∂/∂x) Ψ dx. The book then told me the kinetic energy operator T = p2/2m = -ħ2/2m (∂2/∂x2) I am just think that why isn't it -ħ2/2m (∂/∂x)2 Put in other words, why isn't it the square of the derivative, but...
  24. A

    Kinetic Energy and Work/ Work depends on acceleration?

    1. Problem Statement: A worker lifts a heavy crate vertically 1.0 m in 2.0 s. If she lifts the same crate the same distance in 1.0 s, the work was done by her is A the same. B two times as great. C half as great. D four times as great. E one-fourth as great...
  25. energeticringleader

    Rest, Mass, and Kinetic Energy

    Homework Statement I really don't have a homework question just a thought. Is rest energy "maximum energy" for a particle? As to say a particle at rest has a given energy, so when it is in motion it transfers some mass energy to kinetic energy, where both the mass and kinetic energy together...
  26. F

    Video about pressure in kinetic theory

    Hi, I am looking for a video helping intuition on pressure, in the context of kinetic theory of gases. I remember seeing a video where someone poured a bucketful of little hard balls (lead sinkers for fishing?) onto an electronic scales (a dynamometer, really) showing that this corresponds to...
  27. Eclair_de_XII

    How to balance gravitational energy and kinetic energy?

    Homework Statement "In Fig. 8-33, a runaway truck with failed brakes is moving downgrade at ##130\frac{km}{h}## just before the driver steers the truck up a friction-less emergency escape ramp with an inclination of ##θ=15°##. The truck's mass is ##1.2⋅10^4kg##. What minimum length L must the...
  28. D

    I Storing Kinetic & Mechanical Energy

    How can kinetic or mechanical energy be stored?
  29. TheSodesa

    Maximum change in the kinetic energy of a particle

    Homework Statement Show that the largest possible change in the kinetic energy , ##\Delta E_{kin}##, of a particle of mass ##m## running into another particle of mass ##M## at rest in the lab coordinate system is \Delta E_{kin} = \frac{-4AE_{kin}}{(1+A)^{2}}, where ##A = \frac{M}{m}##...
  30. F

    Elements of plasma kinetic theory, Bittencourt

    Homework Statement Consider the motion of charged particles, in one dimension only, in the presence of an electric potential V ( x). Show, by direct substitution, that a function of the form f=f(1/mv^2 + qV) is a solution of the Boltzmann equation under steady-state conditions. Homework...
  31. R

    Absolute temperature for average translational kinetic energ

    Homework Statement The ammonia molecule (NH3) has a dipole moment of 5.0×10−30C⋅m. Ammonia molecules in the gas phase are placed in a uniform electric field E⃗ with magnitude 1.3×106 N/C . Part A: What is the change in electric potential energy when the dipole moment of a molecule changes...
  32. S

    How Does Velocity Relate to Kinetic Energy in Projectile Motion?

    Hey guys, this question has boggled my mind not because I don't know how to approach it but apparently the method I'm using is incorrect! Question A cannonball with a mass of 150 kg is fired from a cannon. The cannonball leaves the cannon with 447.9 kJ of kinetic energy. The cannon makes an...
  33. M

    Question on work energy and power kinetic energy of an ....

    Homework Statement If the speed of a vehicle increases by 2m/s then it's kinetic energy is doubled. Find out the original speed of the vehicle Homework Equations 1/2(mv^2) The Attempt at a Solution First find out both KE(kinetic energy) taking u(initial vel.) And v(final vel.) And mass as m...
  34. X

    Inelastic Collision: Kinetic Energy vs Momentum

    In an inelastic collision is the change in kinetic energy equal to the difference of final and initial momentum if one of the objects is initially at rest? For example: m1v = (m1+m2)Vf -----> 0 = (m1+m2)Vf - m1v1 1/2(m1+m2)Vf^2 - 1/2m1v^2 = (m1+m2)Vf - m1v1 Or totally wrong? Thanks!
  35. marsupial

    Coefficients of kinetic and static friction in a pulley

    Homework Statement A block of mass ## M_1 ## is on an inclined plane (the plane is inclined at 30 degrees), and is attached with a light cord over a light, frictionless pulley to another mass ## M_2 ##. ## M_1 ## is fixed at 5.00kg, and ## M_2 ## can be varied. When ## M_2 = 3.20 kg ##, ##...
  36. P

    Kinetic friction in an N,T- system only works in tangential?

    Homework Statement Homework Equations F=m*a ΣF(n-direction)= m*a(n)= m*(v^2/ρ) ∑F(t-direction)= m*a(t)\ Ffriction= Fn*coefficient(of friction) The Attempt at a Solution So I tried solving this question and apperently it is way easier than I thought. So I thought the kinetic friction has a...
  37. F

    How to intuitively see the v^2 relation to kinetic energy?

    KE is proportional to v^2. In a gravitational field KE=1/2 m*v^2. It's easy to find mathematically Work=Fd=mad=m(v/t)(v*t)=m*v^2. But how to visualize it or get an intuitively "feel" for this v^2 relationship?
  38. S

    Solve questions on oscillations and kinetic energy

    A spring of spring constant k sits on a frictionless horizontal table, one end of the spring is attached to a wall the other end to a block of mass M= 2kg, also resting on the frictionless table. Another block of mass m=450g moving at a speed of 7m/s collides in-elastically with the block of...
  39. Gummy_Bear

    Kinetic energy of positron and proton

    1.e problem statement, all variables and given/known data Two positrons and two protons are kept on the four corners of a square of side a. Positrons are kept at vertices A and C and protons are kept at B and D. let q denote the charge on both positron as well as the proton. So what is the...
  40. JayaSuria

    Inelastic Collision - Kinetic Energy

    A 6.0kg metal ball moving at 4.0m/s hits a 6.0kg clay ball at rest and sticks to it. The two move at 2.0m/s. a. calculate the kinetic energy of the metal ball before it hits the clay ball. b. calculate the kinetic energy of the metal ball after it hits the clay ball. c. calculate the kinetic...
  41. Vavi Ask

    Kinetic Energy when the Force is Perpendicular to Velocity

    Homework Statement Given, force of constant magnitude, which is always perpendicular to the velocity of the particle & the motion takes place in a plane. What happens to its kinetic energy? Explain. Homework Equations Work energy theorem The Attempt at a Solution According to work energy...
  42. S

    How Do You Calculate the Kinetic Energy of CO, CO2, and SO3 at 276 K?

    Homework Statement Calculate the kinetic energy of CO, CO2, and SO3 at 276 K . Homework Equations KE = (3/2) RT KE= (1/2)(mass)(velocity)^2 The Attempt at a Solution [/B] For CO: First attempt: KE=(3/2)(RT)=(3/2)(8.314 J/mol-K)(276K) = 3441.996 -- So that's wrong Second attempt: Relative...
  43. BlueQuark

    How can kinetic friction force be constant if....?

    As we all know, for the most part, the kinetic friction force is, for the most part, constant. After moving my cup across my table, this thought crossed my mind. If I move my cup across the table with a constant speed, then the force I'm applying must be equal to the kinetic friction force...
  44. J

    Calculate height and velocity given kinetic and potential?

    Homework Statement I have a table that needs to be filled out. In each column, potential and kinetic energy are given, but height and velocity are left blank. Ex: PE = 20 J, KE = 0 J, h = ?, V = ? Homework Equations KE = 1/2mv^2 U = mgh The Attempt at a Solution I'm totally stumped. How can I...
  45. D

    Final Frequency and Kinetic energy change?

    Homework Statement Hi I know my picture has 2 problems, but let's just focus on the first problem parts a and b. So for part a it ask for the final frequency after the ant landed, and part b is the kinetic energy difference. Basically the ant=.01kg, diameter of cylinder is .115m, the weight of...
  46. R

    Kinetic Salt Effect - Size of Ions

    Hello, Throwing out a question to see if anyone has some insight. The kinetic salt effect describes the variation of the rate constant of a reaction with respect to the ionic strength of the solution. The mathematical relationship considers the ionic strength (molality/ion charges) of the...
  47. bebop1

    Kinetic Energy and Collision Question

    Homework Statement Why is there more heat and sound energy produced with a larger collision? Homework EquationsThe Attempt at a Solution Honestly no clue. I would really appreciate any help! Any videos would also help!
  48. gennarakis

    I Quantum Kinetic Energy of Neutrons, Protons and Electrons

    Hi there, I have a problem to solve in Cosmology which says: "Write the formulas for the quantum kinetic energy of neutrons, protons and electrons as well as the formula for the gravitational energy for a neutron star that is comprised of free neutrons, protons and electrons in a ratio of Nn ...
  49. bebop1

    Kinetic Energy and Collision Question

    Is there a threshold of maximum kinetic energy lost when kinetic energy is transferred between two objects through collision? I just cannot find any information on this, any help would be VERY much appreciated.
  50. C

    UHP water jetting and calculating kinetic energy

    If i compress water to 60 ksi, and push it through a 0.015" sharp orifice, then i have another orifice 2 feet before that sudden open to 0.015", what is the velocity of the stream from each orifice?
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