Lecture 8; Momentum, Impulse and Collisions

A 480 kg car moving at 14.4 m/s hits from behind another car moving at 13.3 m/s in the same direction. If the second car has a mass of 570 kg and a new speed of 17.9 m/s, what is the velocity of the first car after the collision? A. 8.94 m/s B. - 8.94 m/s C. 19.9 m/s D. 10.5 m/s

A. 8.94 m/s

Two vehicles with equal magnitudes of momentum traveling at right angles to each other undergo an inelastic collision. The magnitude of momentum for the combined wreck is: A. greater than the magnitude of momentum of either car before collision B. the same as the magnitude of momentum of either car before collision. C. less than the magnitude of momentum of either car before collision.

A. A greater than the magnitude of momentum of wither car before collision

Which one of the following is characteristic of an inelastic collision? A. Kinetic energy is not conserved. B. Total energy is not conserved. C. Total mass is not conserved. D. The change in momentum is less than the total impulse. E. Linear momentum is not conserved.

A. Kinetic energy is not conserved.

Kinetic energy is conserved only in perfectly elastic collisions, but momentum is conserved in all collisions. A. True B. False

A. True

When the force that produces an impulse acts for twice as much time, the impulse is: A. doubled. B. halved C. quadrupled. D. not changed.

A. doubled.

Complete the following statement: Different types of collisions between interacting bodies are categorized on the basis of: A. kinetic energy conservation. B. the magnitude of the forces involved. C. linear momentum conservation. D. the temporal duration of the collision E. mechanical energy conservation.

A. kinetic energy conservation.

Three objects are moving along a straight line as shown in the figure. Taking the positive direction to be to the right, what is the total momentum of this system? 1) 5.00 m/s, 8.00 kg 2) 4.00 m/s, 15.0 kg 3) 2.00 m/s, 3.00 kg A. +14 kg m/s B. -14 kg m/s C. 0 kg m/s D. -106 kg m/s E. +106 kg m/s

B. -14 kg m/s

A ball of clay is thrown against a wall and sticks there. In this process, momentum is not conserved because the clay stops moving. A. True B. False

B. False

A rubber ball moving horizontally at 8.50 m/s hits a brick wall and bounces back with exactly the same speed but in the opposite direction. During this collision, its change in momentum is zero. A. True B. False

B. False

If a force acts perpendicular to an object's direction of motion, that force cannot change the object's kinetic energy or momentum A. True B. False

B. False

In a collision between a small car and a large truck, the car and the truck undergo the same change in their velocities A. True B. False

B. False

When a baseball player hits a home run, the baseball receives a greater impulse from the bat than the bat does from the ball. A. True B. False

B. False

When a moving object hits a stationary object and causes it to move, some of the moving object's kinetic energy is transformed into momentum in the object that was at rest. A. True B. False

B. False

Two objects of equal mass traveling toward each other with equal speeds undergo a head on collision. Which one of the following statements concerning their velocities after the collision is necessarily true? A. Their velocities will be reduced. B. Their velocities may be zero C. They will exchange velocities. D. Their velocities will be zero. E. Their velocities will be unchanged.

B. Their velocities may be zero

The total momentum of a flock of identical birds could be zero only if the birds are: A. taking off from the ground. B. flying in different directions. C. flying in the same direction. D. very tired and coming down to rest.

B. flying in different directions.

Complete the following statement: A collision is elastic if: A. the final momentum is zero B. the total kinetic energy is conserved. C. the final kinetic energy is zero. D. the final velocities are zero. E. the objects stick together.

B. the total kinetic energy is conserved.

Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet? A. half the sum of their original momentums B. zero C. twice the sum of their original momentums D. need more information

B. zero

Complete the following statement: Momentum will be conserved in a two-body collision only if: A. the collision is perfectly elastic B. the kinetic energy of the system is conserved. C. the net external force acting on the two-body system is zero. D. the internal forces of the two body system cancel in action-reaction pairs. E. both bodies come to rest.

C. the net external force acting on the two-body system is zero.

Which one of the following statements concerning momentum is true? A. Momentum is a scalar quantity. B. Momentum is a force. C. The SI unit of momentum is kg ⋅ m2/s. D. Momentum and impulse are measured in the same units. E. The momentum of an object is always positive.

D. Momentum and impulse are measured in the same units.

A primary difference between momentum and kinetic energy is A. none of them B. kinetic energy can cancel; momenta cannot C. either of the above depending on circumstances D. momenta can cancel; kinetic energy cannot.

D. momenta can cancel; kinetic energy cannot.