Momentum conservation Definition and 238 Threads

Homework Statement A rod of length D sits at rest on a friction less table. A ball of mass M strikes the end of the rod with a speed V and rebounds with a speed 3v/4 causing the rod to rotate counterclockwise around a fixed axis at one end. The rotational inertia of the rod is I Homework...

I'm a passout from school taking a gap year. I find the concept of conservation of momentum exceedingly difficult. Each question - and sometimes each part of a question, if a question has different parts - requires us to choose different systems each time. I look at the solution, and think I...

Homework Statement suppose you're sitting on a rotating stool holding a 2kg mass in each outstretched hand, if you suddenly drop the masses, will your angular velocity increase, decrease or remain the same? Homework Equations dL/dt=net torque when net torque is 0, L=constant=Iw therefore...

Homework Statement A block of mass m slides down a wedge of mass M and inclination theta from rest. All the surfaces are smooth. Find the speed of the wedge when the speed of the block w.r.t to wedge is v. Homework Equations V(c.m.)=m1v1+m2v2/(m1+m2) The Attempt at a Solution Conserving...

Homework Statement There is a 4 kg mass that has a speed of 6 m/sec on a horizontal frictionless surface. The mass collides head-on and elastically with an identical 4 kg mass initially at rest. The final speed of the first 4 kg mass is: (a) 0 m/s (b) 2 m/s (c) 3 m/s (d) 6 m/s Homework...

If a ball hits a rod at the top which is pivoted at bottom end then is linear momentum conserved?

Homework Statement Three bodies A,B,C on frictionless surface masses= 1 kg each, Positions at time 0: A is at x=0,. B is at x=1, C is at x=2 (unit is 1 meter). velocities at time 0: A : 1m/s (to the right), B = 0 m/s, C = -1 m/s Assume sizes are uniform, or just ignore the sizes in...

I just want to state that i DID solve the problem. I just seek understanding of it. I'd be really grateful if someone could answer two of my questions at the end of this post. The problem I've solved here is just to show what I'm dealing with. 1. Homework Statement Object 1 is moving towards...

(I hope this post doesn't cross the border into the forbidden realm of quackery and speculation.) I have what seems like a simple question about Special Relativity but I haven’t seen it discussed anywhere, nor has anyone I've asked. Does the nonlinearity of the Lorentz factor provide a way...

A 1 keV fast neutron (relative mass 1) in a moderator collides elastically with a helium atom He (relative mass 4) at rest. What is the maximum amount of energy the neutron can lose? My answer is 16/25 of 1ke but while deriving this answer I simply solved based on the question as if the...

I read that kinetic energy may not be preserved, but momentum must always be preserved. How can that be? If there's a loss in kinetic energy due to friction or heat, the velocities will be reduced thus momentum will be reduced?

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...

Homework Statement I need to find the intial velocity of a ball, given the angle the pendulum bob swings through. I need to derive this equation. [/B] V0=4.43mtotalL1/2{1-cosΔθ}1/2/mball Homework EquationsThe Attempt at a Solution I have barely any attempts since I can't even think where to...

Homework Statement . True or False:[/B] For a completely elastic collision of two isolated masses the energy lost is ½μνr2 Where [SIZE=16px]μ is the reduced mass of the system and νr is the magnitude of relative velocity between the two particles. Homework EquationsThe Attempt at a Solution...

Homework Statement The luminosity of the star is defined as ##\phi = L/4\pi r^2## The photons from the star hits the sail of mass ##M## and cross sectional area ##A##. What's the final velocity of the sail after getting hit by photons for a small time t? Assume the collision is elastic and the...

We have two cylindrical shells (with radii a and b and charges +Q and -Q) along the z-axis. There is a uniform magnetic field (in the positive z-direction) out to radius r from the z-axis. Because of the symmetry, the total field momentum is zero. Suppose we now connect the shells using a wire...

Why ain't momentum conserved when external force acts on the system? Please explain with an example.

Homework Statement So, I need to find the X and Y components of the force in the T section Homework Equations Due the fact that the problem dosn't ask for a specific force I couldn't think in any other equation to use, because even tough there is Pressure and Gravity acting I need to...

Homework Statement The same horizontal force is applied separately to two objects initially at rest on a horizontal, frictionless surface. Object A has less mass than object B. In each case the force is applied for the same length of time. Which of the following statements is true after the...

In general relativity, does momentum conservation mean conservation of 4-momentum or 3-momentum

Homework Statement Let two particles of equal mass m collide. Particle 1 has initial velocity v, directed to the right, and particle 2 is initially stationary. A: If the collision is elastic, what are the final velocities v_1 and v_2 of particles 1 and 2? B: Now assume that the mass of...

Homework Statement A block of mass 200g is suspended through a vertical spring. The spring is stretched by 1.0 cm when the block is in equilibrium. A particle of mass 120g is dropped on the block from a height of 45 cm. The particle sticks to the block after the impact. Find the maximum...

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >[/color] My question is from an exam in analytic mechanics. The question was about an object sliding on inclined plane, the plane's angle is constant, and the plane is free to move along X axis...

1. In the figure shown , a ball of mass m collides perpendicularly on a smooth stationary wedge of mass M , kept on a smooth horizontal plane. If the coefficient of restitution is e , then determine the velocity of the wedge after collision. https://postimage.org/][/PLAIN] Given mass of ball...

Homework Statement A uniform solid sphere of radius R, rolling without sliding on a horizontal surface with an angular velocity ωo, meets a rough inclined plane of inclination θ=60°. The sphere starts pure rolling up the plane with an angular velocity ω. Find the value of ω. Homework...

I often hear that a superconductor can hold a current indefinitely, I have a thought experiment which relates to this claim. Consider a closed square loop of superconducting wire, this wire carries some current. Will the electrons in the circuit transfer momentum and energy to the metal lattice...

Homework Statement A railway waggon of mass m=20t is traveling with v=18km/h. It then hits 10 other stationary railway waggons, with each one having the same mass of m=20t . (Friction is not being considered) Homework Equations a) Assume the 10 railway waggons are connected through strong...

Homework Statement A .01kg bullet is fired into a 1.2kg block hanging from a 1m wire. The bullet exits the block with a speed of 200m/s and the block swings to a height of .2 meters. What is the original velocity of the bullet? What percentage of the original energy of the bullet is no longer...

I remember throwing clay balls at walls in my childhood and observing them stick to the wall. In a more scientific perspective, considering the ball and wall as a system, I can say that the total momentum before collision is greater than 0. But then, after the collision, the kinetic energy of...

When reading lessons on the conservation of momentum, you usually see examples with colliding balls or something to that effect. These examples always seem to fail to mention friction. These balls will always come to a stop due to friction. How is momentum conserved when it is lost to friction...

Homework Statement A uniform rod of length L and mass M hangs at rest from a frictionless pivot. The rod is hit a distance 0.8L below the pivot by a particle of mass m moving perpendicularly to the rod at speed v; the particle sticks to the rod. Following the collision, the maximum angle...

My textbook talks about the average angular speed that ω = angular displacement / time for the angular displacement to take place. So the question is like there is m1v1 = m2v2, can the velocity be instead average angular speed to have the conservation of momentum equation like this? m1ω1 = m2ω2

Homework Statement Particle A has a mass of 1kg and velocity 2x10^8m/s to the right and collides with a stationary particle B that has a mass of 4kg. after the collision, particle A moves to the left with a velocity(v) and particle B moves to the right with a velocity of 1x10^7 m/s. calcuate...

Imagine two equal charges, one at rest and the other moving uniformly. From Special Relativity we know that the electric field of the moving charge is different respect the one of the charge at rest. So the two forces of the interaction do not verify the law of action-reaction and there is a...

This is from text [Introduction to Lagrangian and Hamiltonian Mechanics] on NTNU opencourse. Annnnd... I don't use english as my primary language, so sorry for poor sentences. I can't get two things in here. First, at (1.12) I can't understand how L dot derivated like that. Since I know...

If a car crashes with a stationary tree and comes to stop, we could say that the kinetic energy of the car was converted to heat and that the collision was inelastic. However, conservation of momentum dictates that momentum is still conserved. How would that be possible given that neither the...

I think this is a basic question, at least I would hope so. If two identical motorcycles are going at the same speed but one has a lighter individual. If each individually collides with a stationary object and the driver is ejected. Who will go further and why?

Say there is a man swinging in space on a rope attached to a pivot. The man is rotating at some constant angular speed w. Now he climbs up the rope at some constant speed v. Apparently the angular momentum is conserved. As a result his speed increases. However, how does his speed increase if...

Given a system of charged particles interacting with an EM field. Is the canonical momentum always conserved? If so, what is the associated symmetry? Thanks in advance.

What is the momentum of a ball at the exact point where it comes into contact with a wall?

A uranium-238 atom can break up into a thorium-234 atom and a particle called an alpha particle, α-4. The numbers indicate the inertias of the atoms and the alpha particle in atomic mass units (1 amu = 1.66 × 10−27 kg). When an uranium atom initially at rest breaks up, the thorium atom is...

Homework Statement The mass of a spaceship is 10012 kg. The spaceship is at rest. Then one part of the ship with a mass of 1000 kg is ejected and emerges with a speed of 112 m/s. What is the speed of the other part? Homework EquationsThe Attempt at a Solution I tried: pi=pf mivi=mfv2 10012...

I'm confused about situations involving rotating frames in which the angular momentum is conserved and the initial velocity does not change. I'll make an example. Take a rotating carousel (constant angular velocity) with no friction on it and a ball. At the initial time instant the ball has the...

Homework Statement A bullet leaves the barrel of a gun with a kinetic energy of 90 J. The barrel of the gun is 50 cm long. The gun has a mass of 4 kg, the bullet 10 g. (a) Find the bullets final velocity. (b) Find the bullets final momentum. (c) Find the momentum of the recoiling gun. (d) Find...

I do not get why systems such as the rocket in space are defined as "variable mass" since the mass of the system is not varying. The equation used for such systems $$\sum F^{(E)}=\frac{d\vec{P}}{dt} \tag{1}$$ (sum of external forces on the system equals the change in momentum) holds true only...

Would momentum be conserved on a cart if in one situation it is on an incline and the other it is on a flat surface(assuming it is pushed) I am confused because I thought that since gravity is an internal force, it is a conservative force. But then the final velocity of the cart would be...

Homework Statement Homework Equations I guess kepler's law but most importantly conservation of angular momentum are key here. The Attempt at a Solution [/B] I put down E as the answer, but the solutions have D as the correct answer. Why is this the case? Thanks in advance for the help!

Homework Statement Show that the scatter angles of the photon (θ) and electron (Φ) in the Compton effect are related by the relation: ##cot (θ/2 )=(1+\frac{hf}{mοC^2}) tan(Φ) ## Where f is the frequency of incident photon 2. The attempt at a solution I wrote down the equations of conservation...

Homework Statement A comet in deep space picks up mass as it travels through a large stationary dust cloud. It is subject to a gravitational force of magnitude Mf acting in the direction of its motion. When it entered the cloud, the comet had mass M and speed V. After a time t, it has traveled...

Homework Statement This was a question I came across in my A level physics course: A garage attendant was surprised to be asked to give a lorry a push as the battery was flat. He was even more surprised when he leant on the back of the lorry and the slight movement of the lorry was enough to...