Kinetic energy Definition and 1000 Threads

Homework Statement In a QM problem I must calculate the expectation value of the kinetic energy, namely ##\langle \Psi _c ,\frac{ \hat { \vec p } ^2}{2m} \Psi _c \rangle##. Where ##\Psi _c=ce^{-\alpha x^2}##. Homework Equations ##\int _{-\infty}^\infty \exp \{ -a x^2 +bx \} dx =...

I have been doing some working on braking energies, and have hit a bit of confusion with regards to the kinetic energy of the wheels and tyres. Obviously, the kinetic energy of the moving car itself follows the old rule of 1/2mv2. For a 1000kg car at 30ms that's then 450kJ. I have then...

Hi, I'm new to physics and have some trouble understanding the concept of Kinetic Energy. It's not that I don't understand the definition given to me, I do, but I don't feel the intuition behind the concept. Here's what I understood of the concept : Kinetic energy comes from moving objects (If...

[FONT="Arial"] Homework Statement A body of mass 2.0 kg makes an elastic collision with another body at rest and continues to move in the same direction but with one-fourth of its original speed. What is the mass of the struck body?Homework Equations Conservation of Kinetic Energy EK =...

Homework Statement Hello I've been doing this experiment which is about momentum and kinetic energy. I'm using an air track and using two carts one 3/4 of the way down with 50g weights I will add to it each time I test it this will be the variable i will be changing the cart will stay...

Suppose that we are working with a horizontal string with two masses attached. There is no friction on the floor and we move those two attached masses away from the equilibrium position by an undefined distance. Once the string with those two attached masses passes through the equilibrium...

This is probably a stupid question because the answer is likely "it just is". I am reading Calculus: The elements by Michael Comenetz, and when talking about mQ, he goes on to say "there happens to be advantage in working with 1/2 mQ rather than mQ itself", and then gives the equation k = 1/2...

Homework Statement A roller coaster descends 55m from the top of the first high point to the first low point in the track. The roller coaster converts gravitational potential energy to kinetic energy with an efficiency of 50.0%. What is the velocity of the roller coaster at the bottom of the...

I have two rigid bodies floating in space that are kinematically constrained by a joint (think of a 2 dof link mechanism floating in space). I have a body fixed reference frame on each rigid body plus the global space-fixed reference frame. The first rigid body is in the space-fixed...

1. a) A relativistic proton has a momentum of 10x10^-18 kg*m/s. The rest energy of a proton is 0.150nJ. The kinetic energy of the protoon b) In this situation the speed of the proton is? 2. E=MC^2 P= MV/sqroot(1-(v^2/c^2) K=[MC^2/ sqroot(1-v^2/c^2)]-[mc^2] 3. The algebra in this problem...

Homework Statement A 110 kg football player runs at 2.75 m/s directly into a 125 kg player running 2.60 m/s towards him. What is the kinetic energy of the two players if this is a completely inelastic collision. Homework Equations P = m*v P[SIZE="1"]total = P[SIZE="1"]i -...

Hello, The formula for average kinetic energy of molecule is: k=3/2KT. Can anyone please explain the derivation without using calculus? Thanks, -- Shounak

Homework Statement For the decay " Uranium-232 ---> Thorium-228 + alpha particle ", What is the alpha particle's kinetic energy in the U-232 atom's rest frame? We are given the masses for each one. Homework Equations E = mc^2 The Attempt at a Solution I tried mass(U-232) -...

Homework Statement 1.5ton (1500kg) object is dropped from 20 meters into a bucket with 2.5L of water in it. All the kinetic energy is transferred to the water in form of heat. What is the temperature rise of the water? 2. how much the water temperature rises if the object lifts during it's...

1. Two carts, each of mass M, travel towards each other on a frictionless air track, one with velocity V, and the other with -3V. They collide and stick together. How much kinetic energy is lost in the collision? 2. P = mv, KE=1/2mv2 3. Initial KE of the system is the sum of the kinetic...

When an electron moves through a wire between two terminals on a battery some of its potential energy is converted to kinetic energy. My question is, where does that kinetic energy go once it reaches the other terminal? Some of it is probably converted to heat, but what about the rest of it?

Homework Statement A thin and uniform bar has a length of 2.00 m and weighs 12.0 kg. It is rotating from one end on a pivot 5 times every three seconds. What is its kinetic energy? This is its hint: break the bar up into infinitesimal segments of mass dm and integrate to add up the...

Homework Statement I have to use energy conservation to solve this. So i cannot solve with kinematics "On a windless day, the engine of a 250 g toy rocket exerts 30N of thrust straight upward until it burns out at a height of 165 m" How fast is the rocket moving at 165m? Homework...

Homework Statement A 1kg mass is projected from the edge of a 20m tall building with a velocity of 20 m/s at some unknown angle above the horizontal. What is the kinetic energy (in J) of the mass just before it strikes the floor? Homework Equations K= 1/2 m v^{2} The Attempt at a...

Could someone please check my answers so far for this question as its getting very messy so I'm not sure if I've made a mistake :/ [FONT=verdana]Two particles of masses 2m and m are moving along the x−axis with constant velocities u1i and u2i...

I guess I'm getting old and dumb but I'm having trouble with a basic physics concept, I'm sure you can explain it... Why is kinetic energy 1/2mV^2 and not mV? ***** Example of my confusion no1. Suppose person A has a mass of 1 and a velocity of 10 (on ice skates). Momentum = mV =...

A potential difference of 50 mV is maintained between the ends of a 9.70 m length of wire whose cross section area is 25.0mm^2. The conductivity of the wire is 6.80 x 10^6 (ohm.m)^-1. Determine the rate at which the energy in the wire is transformed into kinetic to thermal energy. 2. Homework...

How can I calculate kinetic energy of a meteor? On what variables it depends? Thanks and sorry for my bad English.

hi all, its been hours that i could not find a decent answer for a 'simple' Q: during a phase change (say, boiling) the temp' doesn't change, as we all know. we also know that the temp' is a measure of the system kinetic energy (KE). im interested to know how the average KE AND its...

a)I used the equation KE=1/2Iw^2 I=mR^2 ---> 1.5x10^30*20000^2 w=2.1*2pi KE=1/2(1.5x10^30*20000^2)(2.1*2pi)^2=5.2x10^40 J t=2.1 rev/s / 1.4x10^-15 rev/s^2=1.5x10^15 seconds 5.2x10^40 J/1.5*10^15 seconds =3.4x10^25 watts B)1.15*10^15 s=1.1*10^18 years I feel like this method is...

Hi all. English is not my native language, so bare with me (joke i found googling the right word). I am from Argentina. My question. If i throw a ball, i have learned it has kinetic energy. But if motion is relative doesn't that mean that my hand has the kinetic energy too? thanks.

Homework Statement I'm trying to understand how this equation was came together, mainly, I hardly understand why velocity is squared, and why there's the constant of '1/2'. Homework Equations In classical mechanics, the kinetic energy of a point object (an object so small that its mass...

Homework Statement Hey everyone, trying to finish up a report and having a problem with getting to the final answer. It is a final report on hydro kinetic energy. We are planning to install a hydro kinetic turbine under a bridge and calculate what the energy output would be in KW. I am...

We recently started going over momentum in my phyics class and we were given this bit of information: ##impulse=FΔt=mΔv=momentum## I noticed that I were to take the integral of both sides with respect to velocity, it would yield ##FvΔt=Fx=(1/2)mv^2## Which is the Work-Kinectic energy...

Homework Statement Here is the problem: http://www.chegg.com/homework-help/questions-and-answers/7-blocks-collide-elastically-frictionless-surface-write-conservation-momentum-relation-thi-q237700Homework Equations There is conservation of momentum involved along with conservation of kinetic...

two automobiles each of mass 1200kg traveling a the same direction. Speed of one automobile is 29.0 m/s and the other is 19 m/s. Regard these automobiles as a system of two particles. a)what is translational energy of center of mass? I found velocity at center of mass which is 24 m/s and...

Regarding the relation between atoms' kinetic energy and the energy levels of their electrons upon excitation: In other words, what really happens when an atom is excited, either by radiation or by collisions, or otherwise ? What are the mechanisms under which the transferred energy goes to...

Homework Statement Find the most probable kinetic energy of an ideal gas molecule. Homework Equations v=sqrt(2RT/M) where v= most probable velocity k= Boltzmann's constant T= temperature of the system M= molar mass of the gas Maxwell's formula of...

Homework Statement A 50 kg mass is pulled at a constant speed up a 20° incline which is 12m long and 4.1m high. μk = 0.32 a) find the work done by tension, T. b) find the work done by friction. c) find the work done against gravity. Homework Equations W = F x D Work = force x...

Homework Statement While merging onto a freeway, a 1900 kg car accelerates from 17 m/s to 33 m/s What power did the engine supply? W = 7.6 x 105 J F = 9500 N Homework Equations P=W/T The Attempt at a Solution Not sure how to find T.

Homework Statement Use the relationship kinetic energy E = p^2/2m to show that the energy E_{0} of an electron of mass m in its lowest energy state is given by E_{0} = h^2/8mL^2 Homework Equations E = p^2/2m E_{0} = h^2/8mL^2 The Attempt at a Solution I've stared at this...

[b]1. Consider an ocean current flowing at 2.5m/s a) How much kinetic energy is contained in a cubic volume of water that measures 1m on each side? The density of seawater is about 1030kg/m3 b) If the flow is perpendicular to one of the cube faces, what is the rate at which the current carries...

Homework Statement Derive the expression for kinetic energy of a classical particle in spherical coordinates. Homework Equations I believe the answer I am supposed to reach is: T=\frac{1}{2} m (\dot{r}^2 + r^2\dot{\theta^2} + r^2\dot{\phi ^2}sin^2\theta) The Attempt at a Solution...

Hello. It's not a homework but it is kind of exercise. I was wondering what's the kinetic energy of water flow (for a certain amount) from a faucet. But I'm not sure if I got it right. So I counted how much volume of water is dropped in 30 seconds. It turned out it's about 5.6liters. m=5.6kg...

A mass m1 = 6.20 kg is moving North with a velocity of v1 = 13.5 m/s when it collides perpendicularly with another mass m2 = 4.40 kg moving East with a velocity of v2 = 8.80 m/s. Mass m1 runs into mass m2 in an inelastic collision and both masses stick together and move off after the collision...

A ball, which has a mass of m1 = 2.50 kg., is moving with a velocity of 8.00 m/s at an angle of 25.0˚ South of West. It collides with a second ball, which has a mass of m1 = 1.20 kg., which is moving with a velocity of 4.75 m/s at an angle of 61.0˚ North of West. They stick together and move as...

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...