Exam 9: Center of Mass and Linear Momentum

Cart A, with a mass of 0.2 kg, travels on a horizontal air track at 3 m/s and hits cart B, which has a mass of 0.4 kg and is initially at rest.After the collision the center of mass of the two cart system has a speed in m/s of:

The plot shows the force acting on an object as a function of time.Over the time the force is applied, the total impulse is:

Bullets from two revolvers are fired with the same velocity.The bullet from gun #1 is twice as heavy as the bullet from gun #2.Gun #1 weighs three times as much as gun #2.The ratio of the momentum imparted to gun #1 to that imparted to gun #2 is:

A rifle of mass M is initially at rest but free to recoil.It fires a bullet of mass m and velocity v (relative to the ground).After firing, the velocity of the rifle (relative to the ground)is:

If a projectile hits a stationary target, and the projectile continues to travel in the same direction,

Two objects, P and Q, have the same momentum.Q can have more kinetic energy than P if it:

When a particle suffers a head-on elastic collision with another particle, initially at rest, the greatest fraction of kinetic energy is transferred if:

Blocks A and B are moving toward each other.A has a mass of 2.0 kg and a velocity of 50 m/s, while B has a mass of 4.0 kg and a velocity of -25 m/s.They suffer a completely inelastic collision.The kinetic energy lost during the collision is:

If the total momentum of a system is changing:

An elastic collision is one in which:

Two spacemen are floating together with zero speed in a gravity-free region of space.The mass of spaceman A is 120 kg and that of spaceman B is 90 kg.Spaceman A pushes B away from him with B attaining a final speed of 0.5 m/s.The final recoil speed of A is:

A very massive object traveling at 10 m/s strikes a light object, initially at rest, and the light object moves off in the direction of travel of the heavy object.If the collision is elastic, the speed of the lighter object is

The momentum of a system of particles is changing at the rate of 0.71 t + 1.2 t², in kg∙m/s.The net force at t = 2.0 s

The direction of the impulse on a struck baseball

For a two-body collision, involving objects with different masses, a frame of reference which has the same velocity relative to the laboratory as does the center of mass of the two objects is:

Block A, with a mass of 4.0 kg, is moving with a speed of 2.0 m/s while block B, with a mass of 8.0 kg, is moving in the opposite direction with a speed of 3.0 m/s.The momentum of the center of mass of the two-block system is:

The center of mass of a system of particles obeys an equation similar to Newton's second law where:

A 75-kg man is riding in a 30-kg cart at 2.0 m/s.He jumps off in such a way as to land on the ground with no horizontal velocity.The resulting change in speed of the cart is:

At the same instant that a 0.50-kg ball is dropped from 25 m above Earth, a second ball, with a mass of 0.25 kg, is thrown straight upward from Earth's surface with an initial speed of 15 m/s.They move along nearby lines and pass without colliding.At the end of 2.0 s the acceleration of the center of mass of the two-ball system is:

The thrust of a rocket is