Kinetic energy Definition and 1000 Threads

I wasn't sure whether this question belonged in relativity or QM, or even just plain classic. This forum seemed the best bet, but I am not using speeds near C - mere Galilean relativity will suffice here. I have two objects, A and B A is moving with velocity V and thus has kinetic energy E...

Look inside the paint doc. My question is why does the paragraph say ...A positive charge q gains kinetic energy as it falls towards the negative plate... However the graph shows that the positive charge q loses kinetic energy... I am confused what am I not understanding?

Homework Statement You observe that after sliding down a distance of 2.61 m along a 5 m long track that is inclined at 20 degrees to the horizontal, a block of wood has a velocity of 0.13 m/s. If the coefficient of kinetic friction between the wood and the surface of the track is 0.40, what...

Kinetic energy of ball sliding down slope with electric field?? Homework Statement As shown in the figure above, a positively charged ball is placed at point A and slides down the slope from rest. The area has a uniform electric field E = 26.1 N/C, pointing to the right. The mass of the...

Homework Statement An electron acquires 3.45x10^(-16) J of kinetic energy when it is accelerated by an electric field in a computer monitor from plate A to plate B. What is the potential difference between the plates, and which plate is at the higher potential? Homework Equations...

A helicopter lifts a 90 kg astronaut 13 m vertically from the ocean by means of a cable. The acceleration of the astronaut is g/12. How much work is done on the astronaut by (a) the force from the helicopter and (b) the gravitational force on her? Just before she reaches the helicopter, what are...

Homework Statement A nucleus contains Z protons that on average are uniformly distributed throughout a tiny sphere of radiues R. Suppose that in an accelerator experiment a positive pion is produced at rest at the center of a nucleus containing Z protons. The pion decays into a positive muon...

Homework Statement A square of side s has a point charge at each corner. They all have the same charge +q, but different masses, m1, m2, m3, and m4, respectively. Initially, all of the charges are held at rest until they are released. Of course, they would repel each other and move away from...

Homework Statement A deuteron, , is the nucleus of a hydrogen isotope and consists of one proton and one neutron. The plasma of deuterons in a nuclear fusion reactor must be heated to about 3.01×108 . What is the rms speed of the deuterons? What would the temperature of the plasma be if the...

Homework Statement Is the kinetic energy of an electron the same in all frames of reference? Homework Equations I think that the kinetic energy of an electron is E = hc / λ. However, I am not sure: I got this from searching Google rather than learning it myself. The Attempt at a...

According to special relativity, velocity cannot be added to another velocity linearly. But I was thinking, what about kinetic energy? K.E. = mv2/2. As velocity increases, the object's mass also increases. The way I see it, the increase in mass "compensates" for the less-than-expected increase...

In classical mechanics, the time derivative of the kinetic energy of a particle is given by the particle velocity multiplied by the force. Specifically, in one dimension, this translates into: (d/dt)(p^2/2m)= −p/m ∂V/∂x I'm unsure how to prove this...

Homework Statement A very small sphere with positive charge 6.00uC is released from rest at a point 1.20cm from a very long line of uniform linear charge density 4.00uC/m.What is the kinetic energy of the sphere when it is 4.80cm from the line of charge if the only force on it is the force...

[b]1. a pile driver of mass 250kg is allowed to fall from rest through a distance of 2m on to a 400kg steel pile to drive it into the ground. Each impact drives the pile into the ground by 150mm. assuming that the pile driver remains in contact with the pile after impact and that momentum is...

Homework Statement A ball with mass m projected horizontally o the end of a table with an initial kinetic energy K. At a time t after it leaves the end of the table it has kinetic energy 3K. What is t? Neglect air resistance. (answer: (2/g)(√K/m) Homework Equations E = 1/2 mv^2 The...

Homework Statement I'm not particularly confident with my calculations and I would appreciate any feed back. A) What is the kinetic energy of an object with: mass = 5lbm velocity = 200 ft/sec B) What is the potential energy of an object with: mass = 5lbm height = 200ft g = 32.2...

Homework Equations a=F/m Ek= 1/2mv^2 --- Not exactly sure how to go through with this.. I tried finding velocity with the given kinetic energy, but am unsure what to do next.

Homework Statement Calculate the kinetic energy of an electron with a wavelength of 1fm Homework Equations DeBroglie's relation E^2=(pc)^2+\left(mc^2\right)^2 The Attempt at a Solution I used debroglies relation to find momentum. plugged that into find E, and then subtracted the...

I have a lab in which a moving marble collides with a still one. What changes could I make to reduce the amount of kinetic energy loss in the collision? The track for the marbles is a piece of card stock paper. I was thinking: -Use two tubes as a track which will reduce the amount of...

Homework Statement 6. A 2.5-kg book slides horizontally and falls from a shelf 3.0m above the floor. How much work does the force of gravity do on the book as it falls 3.0m? F. 1.2 J G. 7.5 J H. 24.5 J J. 73.5 J 7. Which of the following is the minimum amount of work done by a...

Homework Statement a) Calculate the kinetic energy required to accelerate a single proton from a rest position to 0.9999c. The mass of a proton is 1.67*10^-27 Kg. b) Find the ratio of kinetic energy to the energy of a proton at rest Homework Equations Ekrest = mc2 Ek=...

Hi, first post on the forum! We know that kinetic energy is not conserved in an inelastic collision, and how much of the kinetic energy is lost we can find it out through applying conservation of momentum. But one thing that I don't understand is how does the system know exactly how much...

Homework Statement The following is a summaration of a piece of text in my textbook: The setting is two particles moving in one dimension, under mutual forces, so that the equations of motion are (1): m_1 a_1=F and m_2 a_2=-F (a stands for acceleration) F is only a function of...

Homework Statement (see attachment 1) Homework Equations The Attempt at a Solution I have attached my working, the correct answer is (A) but I can't see where I went wrong. Any help is appreciated!

Homework Statement If Inga, the Laboratory Assistant, rolls a spare head down a 4 m ramp because it was spherical and solid and too heavy at 4.5 kg at a speed of 4.5 m/s, what was its total kinetic energy? Homework Equations KE = (1/2) I ω^2 I = (2/5) MR^2 The Attempt at a Solution...

Homework Statement A 30 kg block is slid down an inclined plane 5 m long with a height of 3 m from the floor. If the force of friction is 50 N, find the work done by the friction and the final velocity at the end of the plane. Homework Equations W = F*d mgh = (1/2)mv^2 The Attempt at...

Homework Statement Part 1: Three objects, a solid cylinder, solid sphere, and a hoop all have equal radii and mass. They all roll down the same incline. Which of the following statements is true about the kinetic energy K of the of the objects after they have rolled down the incline and...

In the QM Hamiltonian, I keep seeing h-bar/2m instead of p/2m for the kinetic energy term. H-bar is not equivalent to momentum. What am I missing here?

Ok before we get to number 3, I need to show you what I did for number 2 because this is kind of a two-part problem: PEinitial + KEinitial = PEfinal + KEfinal mgy + (1/2)mvi2 = (1/2)mvf2 gy + (1/2)vi2 = (1/2)vf2 (9.81)(10) + (1/2)(102) = vf2/2 98.1 + 50 = vf2/2 148.1 = vf2/2 2(148.1) = vf2...

Help with Kinetic Energy concept of two masses that move the same distance! I don't understand why the answer to this is B :( Because KE = (1/2)mv2, if they move the same distance and have DIFFERENT masses, the kinetic energies would be different no?

The problem I am working on is: "A student sits on a freely rotating stool holding two dumbbells, each of mass 2.97 kg (see figure below). When his arms are extended horizontally (figure a), the dumbbells are 0.95 m from the axis of rotation and the student rotates with an angular speed of...

Homework Statement Problem with diagram here Homework Equations I=(1/3)MR2 (I believe the formula given in the problem is incorrect since it is pivoting on one end rather than the center of mass) KE=(1/2)Iω2+(1/2)Mv2 L=Iω=MvR The Attempt at a Solution a. True, the velocity is still going in...

Calculate the speed of a proton given its kinetic energy! Homework Statement Find the speed of a proton (mass = 1.67E-27 kg), if its kinetic energy is 145eV. Write your answer correct to three significant figures. Homework Equations W=.5*m*v^2 Proton Mass = 1.67E-27 kg I tried using...

I have seen the derivation of the kinetic energy equation using F=M*v' and E=F*x And I can see how this works, however if you try to do this without thinking about velocity, and only thinking about the rate of change of distance, and the rate of change of rate of change of distance, then the...

I need to know how to find the kinetic energy of ions leaving a charged plate. I figure I can find the electric potential energy, but all i know is the power being supplied to the plate and the plate's cross-sectional area. Any ideas? Thanks in advance!

The problem I am working on is: "Big Ben, the Parliament tower clock in London, has an hour hand 2.70 m long with a mass of 300 kg, and a minute hand 4.20 m long with a mass of 100 kg (see figure below). Calculate the total rotational kinetic energy of the two hands about the axis of rotation...

Homework Statement A 0.125kg basketball is rolling w/out slipping on a horizontal table at 4.50 m/s when it rolls off the edge and it falls to the floor, 1.10 m below. What is the rotational kinetic energy of the ball right before hitting floor?Homework Equations KE rot: .5 I w^2 KE...

Hi! The kinetic formula are EK=1/2*m*v^2. But how do we find it?

I'm confused with this topic. However, I think I know a bit. There's something to do with the temperature and it affects the energy of the molecules. Can someone help?

Task So I am writting a lab, and one of the testable questions required me to come up with a relationship between position and kinetic energy. In the lab a cart is released on a ramp and the end point of the cart is used as the reference point (h=0). We formed a position time graph and we...

Ok so I have got the right answer to my calculation however I do not understand part of it, here is the question... Q2: The rollercoaster car from Task 1 Q2 above is initially traveling at 6.5m/s at point A in the diagram below. Assuming negligible frictional forces as previously, what will...

Homework Statement In the problem, a hanging block, m, is attached to a pulley that is mounted on a horizontal axle with negligible friction. The pulley has a mass of M=75kg and a radius of R=6.0cm. The mass of the hanging block is m=1kg. The block is released from rest at a height above the...

Homework Statement You hold up an object that consists of two blocks at rest, each of mass M = 3 kg, connected by a low-mass spring. Then you suddenly start applying a larger upward force, of constant magnitude F = 94 N (which is greater than 2Mg). Some time later, the blocks have moved...

A uniform marble rolls down a symmetric bowl, starting from rest at the top of the left side. The top of each side is a distance above the bottom of the bowl. The left half of the bowl is rough enough to cause the marble to roll without slipping, but the right half has no friction because it...

Homework Statement Object A of mass 10 kg moving at 10 m/s [E] interacts with (but does not touch) Object B of mass 8 kg moving at 12 m/s [N]. What is the minimum possible kinetic energy of the system after the collision? Homework Equations M1V1o + M2V2o = M1V1f + M2V2f KE = (.5)(m)(v2)...

Homework Statement A car (of constant mass) doubles its kinetic energy while driving down a hill sloped at 45º. The factor by which its momentum changes is answer is 1.4?

Homework Statement The figure below shows a thin, uniform bar whose length is L and mass is M and a compact hard sphere whose mass is m. The system is supported by a frictionless horizontal surface. The sphere moves to the right with velocity , and strikes the bar at a distance 1/4L from the...

Homework Statement A ball rolls without slipping down incline A, starting from rest. At the same time, a box starts from rest and slides down incline B, which is identical to incline A except that it is frictionless. Which arrives at the bottom first? (a) The ball arrives first. (b) The...

In my textbook, Joule's apparatus (two blocks falling from height h turn a paddle that stirs and increases the internal energy of water) is claimed to convert the potential energy of the two blocks into internal energy that can be measured by the increase in temperature of the water... but what...

Homework Statement A dynamics cart 1 ahs a mass of 1.8 kg and is moving with a velocity of 4.0 m/s[right] along a frictionless track. Dynamics cart 2 has a mass of 2.2 kg and is moving at 6.0 m/s[left]. The carts collide in a head-on elastic collision cushioned by a spring with spring constant...