ch. 7
A 2.0-kg ball moving eastward at 3.0 m/s suddenly collides with and sticks to a 4.0-kg ball moving northward at 2.0 m/s. What is the magnitude of the momentum of this system just after the collision?
10 kg ∙ m/s
A tiger is running in a straight line. If we double both the mass and speed of the tiger, the magnitude of its momentum will increase by what factor?
4
If you want to double the momentum of a gas molecule, by what factor must you increase its kinetic energy?
4
A 5-kg ball collides inelastically head-on with a 10-kg ball, which is initially stationary. Which of the following statements is true? (There could be more than one correct choice.)
A) The magnitude of the change of velocity the 5-kg ball experiences is greater than that of the 10-kg ball. D) The magnitude of the change of the momentum of the 5-kg ball is equal to the magnitude of the change of momentum of the 10-kg ball.
If a quantity you calculated had units of kg ∙ m/s, what type of quantity could it be? (There could be more than one correct choice.)
A) momentum D) impulse
Which of the following quantities are units of impulse? (There could be more than one correct choice.)
C) kg ∙ m/s D) N ∙ s
Which of the following quantities are units of momentum? (There could be more than one correct choice.)
C) kg ∙ m/s D) N ∙ s
You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You have two choices about what to do with the ball: either catch the ball or deflect it back toward your friend with the same speed as it was originally thrown. Which choice should you make in order to maximize your speed on the skateboard?
Deflect the ball back.
A very light ping-pong ball moving east at a speed of 4 m/s collides with a very heavy stationary bowling ball. The Ping-Pong ball bounces back to the west, and the bowling ball moves very slowly to the east. Which object experiences the greater magnitude impulse during the collision?
Neither; both experienced the same magnitude impulse.
Consider two less-than-desirable options. In the first you are driving 30 mph and crash head-on into an identical car also going 30 mph. In the second option you are driving 30 mph and crash head-on into a stationary brick wall. In neither case does your car bounce back from the thing it hits, and the collision time is the same in both cases. Which of these two situations would result in the greater impact force on your car?
None of the above choices are correct.
A firecracker explodes in midair and breaks up into many fragments. Which of the following statements are true regarding conditions immediately before and immediately after the explosion:I. The total momentum of the fragments is equal to the original momentum of the firecracker.II. The total kinetic energy of the fragments is equal to the original kinetic energy of the firecracker.
Statement I only
a small car meshes with a large truck in a head-on collision. Which of the following statements concerning the momentum during the collision are correct? (There could be more than one correct choice.)
The momentum of the car-truck system is conserved, but the momentum of each one separately is not conserved.
A rocket explodes into two fragments, one 25 times heavier than the other. The magnitude of the momentum change of the lighter fragment is
The same as the momentum change of the heavier fragment.
A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the magnitude of the average force during the collision is correct?
The small car and the truck experience the same average force.
A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the magnitude of the momentum change during the collision is correct? (There could be more than one correct choice.)
The small car and the truck experience the same magnitude momentum change.
Three cars, car X, car Y, and car Z, begin accelerating from rest at the same time. Car X is more massive than car Y, which is more massive than car Z. The net accelerating force exerted on each car is identical. After 10 seconds, which car has the most amount of momentum?
They all have the same amount of momentum.
In a collision between two unequal masses, which mass receives a greater magnitude impulse?
They receive equal impulses.
In the figure, determine the character of the collision. The masses of the blocks, and the velocities before and after, are shown. The collision is
completely inelastic.
In a game of pool, the white cue ball hits the #5 ball and stops, while the #5 ball moves away with the same velocity as the cue ball had originally. Both balls have the same mass. This type of collision is
elastic.
Identical forces act for the same length of time on two different objects. The magnitude of the change in momentum of the lighter object is
exactly equal to the magnitude of the change in momentum of the larger mass.
In an inelastic collision involving an isolated system, the final total momentum is
exactly the same as the initial momentum.
There must be equal amounts of mass on both sides of the center of mass (or center of gravity) of a system.
false
The momentum of an isolated system is conserved
in both elastic and inelastic collisions.
A railroad car collides with and sticks to an identical railroad car that is initially at rest. After the collision, the kinetic energy of the system
is half as much as before.
In the figure showing an isolated system, determine the character of the collision. The masses of the blocks, and the velocities before and after, are shown. The collision is
not possible because momentum is not conserved.
An egg falls from a bird's nest in a tree and feels no effects due to the air. As it falls,
only its mechanical energy is conserved.
On a horizontal frictionless air table, a puck runs into an ideal horizontal spring that is fastened to the table. The puck compresses the spring by 15 cm before coming to rest. During the compression process, which quantities are conserved?
only the mechanical energy (kinetic plus potential) of the puck
) In the figure, determine the character of the collision. The masses of the blocks, and the velocities before and after, are shown. The collision is
perfectly elastic.
If you want to double the kinetic energy of a gas molecule, by what factor must you increase its momentum?
sqrt2
Two friends are standing on opposite ends of a canoe that is initially at rest with respect to a frictionless lake. The person in the front throws a very massive ball toward the back, and the person in the back catches it. After the ball is caught, the canoe is
stationary.
A rubber ball and a lump of clay have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hit. The clay sticks to the wall. Which one of these objects experiences the greater momentum change?
the ball
Two objects of different mass have equal, non-zero kinetic energies. Which object has the greater magnitude momentum?
the heavier object
A rubber ball bounces off of a wall with an initial speed v and reverses its direction so its speed is v right after the bounce. As a result of this bounce, which of the following quantities of the ball are conserved? (There could be more than one correct choice.)
the kinetic energy of the ball
Two objects of different masses have momentum of equal, non-zero magnitude. Which object has more kinetic energy?
the lighter object
A very elastic rubber ball is dropped from a certain height and hits the floor with a downward speed v. Since it is so elastic, the ball bounces back with the same speed v going upward. Which of the following statements about the bounce are correct? (There could be more than one correct choice.)
the magnitude of the ball's momentum was the same just before and just after the bounce.
During World War I, Germany used a "Big Bertha" cannon to hurl shells into Paris 30 miles away. This gun also had a very long barrel. What was the reason for using a long barrel in these guns?
to allow the force of the expanding gases from the gunpowder to act for a longer time
