Kinetic energy Definition and 1000 Threads

A 2-kg block is attached to a horizonal ideal spring with a spring constant of 200 N/m. When the spring has its equilibrium length the block is given a speed of 5 m/s. What is the maximum elongation of the spring? Is not the solution simply: 1/2kx2 = 1/2mv2 x = (mv2/k)0.5 x = 0.5 m...

Homework Statement A uniform solid sphere of mass M and radius R has a light, thin metal spike driven through it, so it is free to turn about this spike. So imagine a bowling ball on a stick that is free to rotate about this stick. A bullet of mass m is fired at speed v into the ball at a...

Homework Statement In a simple model of the wind speed associated with hurricane Emily, we assume there is calm eye 18.8 km in radius. The winds, which extend to a height of 4000 m, begin with a speed of 303.0 km/hr at the eye wall and decrease linearly with radial distance down to 0 km/hr at a...

What happens if a ball goes from rolling on a surface to a frictionless surface? I know friction is required for the ball to roll, so would the rotational energy be transformed into translational energy (the ball goes faster without rolling), or does something else happen? Thanks!

Homework Statement You are given Force as a function of distance (F vs x). Find the change in kinetic energy from $x=a $ to $x=b$. Homework Equations see attempt solution conservation of energy equations The Attempt at a Solution Since F = -dU/dx we get the integral of F = U...

Homework Statement In reference frame S', two protons, each moving at .500c, approach each other head-on. a) calculate the total kinetic energy of the two protons in frame S'. b) Calculate the total kinetic energy of the protons as seen in the reference frame S, which is moving with one of the...

Homework Statement A solid cylinder is rolling without slipping. What fraction of its kinetic energy is linear? Homework Equations Ke=\frac{mv^2}{2}+\frac{I(v/r)^2}{2} The Attempt at a SolutionKe=\frac{mv^2}{2}+\frac{(v/r)^2}{2}*\frac{(mr)^2}{2} Ke=\frac{3(mv)^2}{4} Linear Ke...

A box slides down a 30° ramp with an acceleration of 1.20 m/s^2. Determine the coefficient of kinetic friction between the box and the ramp ok so the only equations I know are μk= Fk(kinetic friction)/Fn(normal) and that Fn=mass x gravity so i don't know how to get Fk or mass... so help on...

How can you tell the difference between kinetic energy and momentum? I know KE is a scalar and momentum is a vector but physically how do they differ? I don't seem to have a full intuitive understanding. I think I do, but I am unsure. I understand the difference quantitatively, KE= (1/2)mv^{2}...

Okay, so I'm at conundrum with my physics textbook and I cannot seem to understand a few concepts. Allow me to elaborate. 1. Why is the total momentum of a firecracker sliding on ice the same before and after it explodes? Shouldn't the explosion cause the momentum to increase since the...

Homework Statement (NOTE: I solved the first two parts of this problem, but I included it anyway so you have background knowledge for the third question) The average kinetic energy of an electron in a ground-state helium atom is 2.4x10^3 kJ/mol. A. What is the corresponding electron...

Say you're given a function that represents the kinetic energy of some object, what would you have to do to derive the force from that function? I know that for motion along a straight line a conservative force F(x) is the negative derivative of its associated potential energy function U, but...

Say you're given a function that represents the kinetic energy of some object, what would you have to do to derive the force from that function? I know that for motion along a straight line a conservative force F(x) is the negative derivative of its associated potential energy function U, but...

Hello, Please i have a question about the internal energy: The Internal Kinetic energy is the motion of molecules and it's a random motion. But at macroscopic level the whole object formed by those molecules move in a same direction? how it can be? In a flowing fluid not static? thank you

Hey guys, I am in a teaching assistant in another 8th grade science class for my 2nd field experience in a title 1 school. The teacher is really struggling(*) to explain to the students the difference between Mechanical and Kinetic Energy. The book their using defines Mechanical Energy as...

Homework Statement Charged particles such as protons are accelerated to high velocities and are allowed to collide with atomic nuclei to probe their internal structure. The electric potential outside of a point charge Ze. A) A lead nucleus (Z - 82) is approximately described as a sphere of...

Hi friends, I have an issue in solving a Kinetic energy problem during collision. Please Help me in solving this. Thank you all in advance. The problem is as: https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-prn2/1375160_1432382953655477_313625437_n.jpg Attempt...

Homework Statement Two closed containers A and B contain equal number of moles of ideal gases GD (diatomic)and GM (Monoatomic) ,respectively. Q .1 a) If the temperature of gases are same,which of them has more average translational kinetic energy ? b) Which of them has more...

Hi All, I have a very simple question on a calculation, I would not doubt it correctness if it were not for the fact I am told by a colleague it is wrong, and I cannot see why (good job college times are gone). We have a cylinder of length L, density $$\rho$$ constant along the cylinder, one...

Homework Statement Two iceboats hold a race on a frictionless horizontal lake. The two iceboats have masses m and 2m. Each iceboats has an identical sail, so the wind exerts the same constant force F on each boat. The two ice boats start from rest and cross the finish line a distance s away...

K'sys=1/2MtotalVcm2+1/2\muVreli2 I understand this equation represents the total kinetic energy in a reference frame. What I'm not getting out of this is the overall concept. I understand that the first part of the equation is supposed to represent the total kinetic energy required to...

What are my units when finding % diff. In kinetic energy? Homework Statement Phrank (36.4kg) runs at 2.2 m/s and jumps onto a large stationary skateboard (2.3kg) on which Phrancine (22.7kg) is sitting. After the collision, Phrank, Phrancine, and the skateboard move at 1.3 m/s. Find the...

Homework Statement Homework Equations The Attempt at a Solution KEi + PEi = KEf 2.4 x 10-19 + e(1) = KEf KEf = 4.002 x 10-19 J So option c would be correct, right? Thank you in advance.

The problem asks to show that the kinetic energy operator is Hermitian. The operator is given as T= -h^2/2mΔ but I know I can also write it as p^2/2m which would be (- ih∇)(-ih∇). My main question is if I can prove this in 1-D so that T=(-h^2/2m)d^2/dx^2 does that generalize to...

E is finite and V is infinite, So T should be negative infinite

Hello everyone, I've run across an interesting Newtonian physics problem that I'd like some input on. The problem begins with a rotating object. Let's assume it is a slender rod rotating about one end with a given mass (m), length (L) and rotational speed (ω). This results in the rod having...

Homework Statement A container having a volume of 1m^3 holds 5 moles of helium gas at 50C. If the helium behaves like an ideal gas, the rms translational kinetic energy is? Homework Equations Total E= 3/2 nRTThe Attempt at a Solution I tried solving this question using this equation, but I did...

Homework Statement What is the maximum possible kinetic energy (keV) of a Compton electron and the corresponding minimum energy of a scattered photon resulting from scattering of a) 100 keV photon b) 1 MeV photon Homework Equations Δλ = 0.24(1-cosθ) The Attempt at a...

I have found that the kinetic energy term for each mass on a coupled (by a spring) pendulum has no \dot{y} terms, as in the the masses do not move in the y direction at all. What am I missing here? I know they are connected, but in the first normal mode, both masses should move like regular...

Hi, I'm learning about momentum and kinetic energy and I wanted to know if the following relationships are true. I think they are true, but I am not sure: If kinetic energy goes down and mass stays constant, momentum goes down If kinetic energy stays constant and mass goes down, momentum...

Show that the kinetic energy of the Earth after a collision can be ignored (stuck & desperately need help)? A ball of mass m2 is dropped and bounces off the floor. If the impact is viewed as an elastic collision between the ball and the earth, show that the kinetic energy of the Earth after the...

If I hit a solid brick wall with a 2kg hammer moving 2m/s, the initial KE would be 4J. Which means the work done would be 4J. But W=F•d says the work is 0 since the hammer comes to a complete stop at the wall without any displacement. ?

If I throw a ball vertically upwards from the surface of the earth, the upward motion slows due to gravity. At the ball's highest point, I have placed a repositioned platform for the ball to rest on; so it sits motionless, perched above the surface of the earth. When the ball began it's...

Homework Statement Write an expression E for the average kinetic energy of Helium atoms using the Boltzmann constant. Homework Equations PV = nRT PV = \frac{1}{3}mN\overline{c^2} k = \frac{R}{N_A} [P - Pressure ; V - Volume ; m - Mass of an atom ; N - Number of atoms ; others have...

why is force equal to rate of change in momentum rather than rate of change in kinetic energy. If we consider time is 1 sec,and if we consider an object is moving with particular velocity V1 and a force F is applied to change the velocity to V2, then according to Newton the force applied is...

Homework Statement A 15 kg block slides along a horizontal frictionless surface 3.0 m above the ground at a constant speed of 2.0 m/s. The block then slides down an incline that makes an angle of 35° with the horizontal and has a coefficient of kinetic friction equal to 0.30. After reaching...

I tried to look this up on the internet. I know there is a book about it but I forgot its title. I know that you can prove that the kinetic energy should be proportional to velocity squared by saying that this is the only Galilean invariant definition of kinetic energy. Can someone help me...

Too familiar with Bose Hubbard model, but suddenly got stuck by a simple question: Why is the kinetic term (to be precise should be single body part) negative?

Homework Statement An object of mass m = 2.3 ± 0.1 kg is moving at a speed of v = 1.25 ± 0.03 m/s. Calculate the kinetic energy (K =(1/2)mv2) of the object. What is the uncertainty in K?Homework Equations Δz = |z| ( Δx/x + Δy/y ) - Multiplication Δz = n (xn-1) Δx - Power The Attempt at a...

Consider a hypothetical particle with no mass (like a neutrino or photon, in that sense), but with pure charge. Consider this pure charge being accelerated in an electric field. Is there any meaning in associating kinetic energy to this charge as it accelerates to a region of lower...

Hello everybody, I am a first year student and I have a question that I am not sure if I can answer. A radioactive isotope of Tin(50), with 85 neutrons in its nucleus and without any electrons bound to it, undergoes a beta minus decay. The electron pops into existence, 10-15m from the center of...

Homework Statement A disk with a mass of 4kg and a radius of 2m is free to rotate around an axis that passes through the center of the disk and perpendicular to the plane of the disk. The rotational kinetic energy of the disk is increasing at a constant rate of 20 J/rad; that is, the energy...

Homework Statement Two masses, one of 20kg and the other of 40kg, are pushed using the same force on the same distance. What is the ratio of the kinetic energy? (Kinetic energy of 20kg/kinetic energy of 40kg) Homework Equations Ek=mv^2 F=ma v=at The Attempt at a Solution So, I...

Hi my name is Bruno, I'm 19, I'm currently finishing my 12nd grade on arts. I'm annoyed because no one I know can properly discuss the Mpemba effect with me. So, I'll go as fast as I can on this. The scenario. We have a cup of water let's say for example at 80 degrees Celsius ...

I am doing the integral DK = ∫pdv = mv/(√1-v2/c2)dv , in the same way as they do the ∫Fds = ∫mvdv if you separate the integrals. Where is my mistake and istead of (γ-1)mc2 I get -mc2/γ . I know that I am mistaken, I did see some equations but I don't get the 'theoretical' part.

This isn't a homework problem, but something that has being buzzing in my head. I've been thinking about it cause at huge distances from Earth g changes and also in what happens for really dense objected and small things could change too. The real equation for gravity no matter which body...

Hello, I was just wondering why the integral of force over dx becomes kinetic energy

Homework Statement A 60kg ice skater is spinning around at 300 degrees per second. His radius of gyration is .5m. As he pulls his arms in he does 300 J of work. i.What is his initial kinetic energy? ii.What is his final kinetic energy ? iii.Assuming that his new radius of gyration is .32m...

Homework Statement A hoop with mass m= 10 kg, radius r=0.6 m, and moment of inertia I=mr^2 is rolling without slipping with a linear velocity of 8.5 m/s. What is the total kinetic energy (in J). Homework Equations K=1/2 m v^2 Kr=1/2 I ω^2 The Attempt at a Solution The kinetic...

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 =...