Physics Chapter 6 Test 2

Which has a greater momentum: a heavy truck at rest or a moving skateboard?
a)The heavy truck at rest.
b)Both have the same momentum.
c)The moving skateboard.
d)Both have zero momentum.

c)The moving skateboard.

A slowly moving ship can have a greater momentum than a fast-moving racing car when _______.
a)its mass is greater than the mass of the car
b)its mass times velocity is greater than that of the car.
c)it drifts toward a distant port.
d)its speed is greater than the speed of the car.

b)its mass times velocity is greater than that of the car.

Distinguish between force and impulse.
a)Force and impulse are the same.
b)Impulse is force times a time interval.
c)Impulse is force per time interval.
d)Force is impulse times a time interval.

b)Impulse is force times a time interval.

An impulse can be increased by
a)increasing the force or increasing the time interval.
b)maintaining the force and decreasing the time interval.
c)decreasing the force and decreasing the time interval.
d)decreasing the force and maintaining time interval.

a)increasing the force or increasing the time interval.

The quantity that is called impulse can be measured by the _______.
a)addition of force and time.
b)product of force and time.
c)difference between force and time.
d)how long the force acts compared to the amount of time

b)product of force and time.

How is the impulse -momentum relationship related to Newton’s second law?
a)F=ma=mΔv/Δt, so Ft=Δ(mv)t
b)F=ma=mΔv/Δt, so F=Δ(mv)
c)F=ma=mΔv/Δt, so Ft=Δ(mv)
d)F=ma=mΔvΔt, so F/t=Δ(mv)

c)F=ma=mΔv/Δt, so Ft=Δ(mv)

To impart the greatest momentum to an object, you must
a)exert the greatest force over the shortest time.
b)exert a force over the greatest time.
c)exert the greatest force over the longest time.
d)exert the greatest force.

c)exert the greatest force over the longest time.

When you are struck by a moving object, is it favorable that the object makes contact with you over a short time or over a long time?
a)Short contact time increases the magnitude of the average force and is favorable.
b)Short contact time decreases the magnitude of the average force and is favorable.
c)Long contact time decreases the magnitude of the average force and is favorable.
d)Long contact time increases the magnitude of the average force and is favorable.

c)Long contact time decreases the magnitude of the average force and is favorable.

Why is a force that is applied for a short time more effective in karate?
a)The average force is independent of the time.
b)The average force becomes zero for short times.
c)The average force is decreased.
d)The average force is increased.

Why is a force that is applied for a short time more effective in karate? Why is a force that is applied for a short time more effective in karate? The average force is independent of the time. The average force becomes zero for short times. The average force is decreased. The average force is increased.

Is it correct to say that, if no net impulse is exerted on a system, then no change in the momentum of the system will occur?
a)Sometimes.
b)Yes, always.
c)Almost always.
d)No, never.

b)Yes, always.

What does it mean to say that momentum is conserved?
a)It means momentum does not change.
b)It means momentum is zero.
c)It means the change in momentum is equal to the impulse.
d)It means the net momentum is zero.

a)It means momentum does not change.

When two vehicles collide, momentum is conserved _______.
a)if the collision is elastic
b)only if deformation of either vehicle does not occur.
c)if the collision is inelastic.
d)whether the collision is elastic or inelastic.

d)whether the collision is elastic or inelastic.

When a big fish swims into an oncoming smaller fish and swallows it, the momentum of the two-fish system _______.
a)remains the same.
b)decreases.
c)increases.
d)converts to spurious motion.

a)remains the same.

Railroad car A rolls at a certain speed and makes a perfectly elastic collision with car B of the same mass. After the collision, car A is observed to be at rest. How does the speed of car B compare with the initial speed of car A?
a)The speed of car B is equal to the initial speed of A.
b)The speed of car B is zero.
c)The speed of car B is twice the initial speed of car A.
d)The speed of car B is half the initial speed of car A

a)The speed of car B is equal to the initial speed of A.

If the equally massive cars of the preceding question stick together after colliding inelastically, how does their speed after the collision compare with the initial speed of car A?
a)Their speed is equal to the initial speed of car A.
b)Their speed is half the initial speed of car A.
c)Their speed is twice the initial speed of car A.
d)Their speed is zero.

b)Their speed is half the initial speed of car A.

When a falling firecracker explodes, the momenta of its pieces _______.
a)vectorally add up to equal the initial momentum of the firecracker
b )disintegrate
c)is conserved only if the fragments eject in one direction
d)illustrate a case where momentum is not conserved

a)vectorally add up to equal the initial momentum of the firecracker

What is the momentum of an 7.8-kg bowling ball rolling at 2.6m/s ?
Momentum = mv

p = 20 kg⋅m/s

What impulse occurs when an average force of 15N is exerted on a cart for 2.6s ?
Impulse = Ft

p = 39 kg⋅ms

A same-size iron ball and wooden ball are dropped simultaneously from a tower and reach the ground at the same time. The iron ball has a greater
a)speed.
b)acceleration.
c)momentum.
d)all of the above
e)none of the above

c)momentum.

The speed of a 4-kg ball with a momentum of 12 kg m/s is
a)3 m/s.
b)4 m/s.
c)48 m/s.
d)12m/s
e)none of the above

a)3 m/s.

A large heavy truck and a small baby carriage roll down a hill. Neglecting friction, at the bottom of the hill, the baby carriage will likely have
a)less momentum.
b)more momentum.
c)about the same momentum.

a)less momentum.

The total momentum of a flock of identical birds could be zero only if the birds are
a)taking off from the ground.
b)very tired and coming down to rest.
c)flying in the same direction.
d)flying in different directions.

d)flying in different directions.

A motorcycle of mass 100 kilograms slowly rolls off the edge of a cliff and falls for three seconds before reaching the bottom of a gully. Its momentum upon hitting the ground is
a)1,000 kg m/s.
b)2,000 kg m/s.
c)3,000 kg m/s.
d)4,000 kg m/s.
e)9,000 kg m/.

c)3,000 kg m/s.

It is correct to say that impulse is equal to
a)momentum.
b)velocity multiplied by time.
c)force multiplied by the distance it acts.
d)a corresponding change in momentum

d)a corresponding change in momentum

Padded dashboards in cars are safer in an accident than non-padded ones because passengers hitting the dashboard encounter
a)shorter time of contact.
b)lengthened time of contact.
c)increased momentum.
d)decreased impulse.

b)lengthened time of contact.

Compared with falling on a stone floor, a wine glass may not break when it falls on a carpeted floor because the
a)carpet provides a smaller impulse and a longer time.
b)carpeted floor provides a smaller impulse.
c)stopping time is shorter on the carpet.
d)stopping time is longer on the carpet.

d)stopping time is longer on the carpet.

If you can’t avoid being hit by a fast-moving object, you’ll suffer a smaller contact force if you can extend that force over a
a)longer time
b)shorter time.
c)both the same

a)longer time

Whether a truck comes to a stop by crashing into a haystack or a brick wall, the stopping force is
a)both the same
b)greater with the haystack.
c)greater with the brick wall.

c)greater with the brick wall.

Whether a truck comes to a stop by crashing into a haystack or a brick wall, the impulse is
a)both the same
b)greater with the haystack.
c)greater with the brick wall.

a)both the same

A tiny gun made of a strong but very light material fires a bullet more massive than the gun itself. For such a weapon
a)recoil problems would be lessened.
b)both conservation of energy and momentum would not hold.
c)conservation of energy would not hold.
d)conservation of momentum would not hold.
e)the target would be safer than the shooter.

e)the target would be safer than the shooter.

A cannon recoils while firing a cannonball. The speed of the cannon’s recoil is relatively small because the
a)momentum is mainly concentrated in the cannonball.
b)force against the cannon is smaller than against the ball.
c)momentum of the cannon is smaller.
d)cannon has much more mass than the cannonball.

d)cannon has much more mass than the cannonball.

A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the same amount of time. Compared with the force that stops the car, the force needed to stop the truck is
a)greater.
b)the same.
c) smaller.

a)greater.

Freddy Frog drops vertically from a tree onto a horizontally-moving skateboard. The reason he doesn’t slip off the skateboard is due to
a)inertia in motion.
b)momentum change.
c)friction between his feet and the board.

c)friction between his feet and the board.

You’re driving down the highway and a bug spatters into your windshield. Which undergoes the greater change in momentum during the time of contact?
a)your car
b)the bug
c)both the same

c)both the same

An astronaut floating alone in outer space throws a baseball. If the ball moves away at 20 m/s, the astronaut will
a)move in the opposite direction at 20 m/s.
b)move in the opposite direction at a lower speed.
c)move in the opposite direction at a higher speed.
none of the above

b)move in the opposite direction at a lower speed.

A 5000-kg freight car moving at 2 m/s collides with a 10,000-kg freight car at rest. They couple upon collision and move away at
a)2/3 m/s.
b)2 m/s.
c)1/3 m/s.
d)1 m/s.

a)2/3 m/s

A 5000-kg freight car collides with a 10,000-kg freight car at rest. They couple upon collision and move at 2 m/s. What was the initial speed of the 5000-kg car?
a)6 m/s
b)8 m/s
c)5 m/s
d)4 m/s
e)none of the above

a)6 m/s

A red car has a head-on collision with an approaching blue car with the same magnitude of momentum. A green car driving with the same momentum as the other cars collides with an enormously massive wall. Which of the three cars will experience the greatest impulse?
a)red car
b)green car
c)blue car
d)all the same

d)all the same

Two vehicles with equal magnitudes of momentum traveling at right angles to each other undergo an inelastic collision. The combined wreck moves in a direction
a)at some angle other than 45 degrees.
b)parallel to either of the cars before collision.
c)at 45 degrees to the direction of either car before collision.

c)at 45 degrees to the direction of either car before collision.

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)less than the magnitude of momentum of either car before collision.
b)the same as the magnitude of momentum of either car before collision.
c)greater than the magnitude of momentum of either car before collision.
d)none of the above

c)greater than the magnitude of momentum of either car before collision.

A cannonball following a parabolic path explodes into fragments. The momentum of the fragments
a)continue along the path as if the explosion didn’t occur.
b)cancels to zero by vector addition.
c)both of these
d)neither of these

a)continue along the path as if the explosion didn’t occur.

When a vertically falling firecracker bursts, the vector sum of momentum fragments
a)in the horizontal direction cancels to zero.
b)in the vertical direction equals the momentum of the firecracker before bursting.
c)both of these
d)neither of these

c)both of these

In which is momentum conserved: an elastic collision or an inelastic collision?
a)Momentum is conserved only in inelastic collisions.
b)Momentum is conserved in elastic and inelastic collisions.
c)Momentum is conserved in neither elastic nor inelastic collisions.
d)Momentum is conserved only in elastic collisions.

b)Momentum is conserved in elastic and inelastic collisions.

When a cannonball is fired, the momentum of the system (cannon + cannonball) is conserved if
a)the momentum of the cannon is zero.
b)the momentum of the cannon is equal to the magnitude of the momentum of the cannon ball and points in the opposite direction.
c)the momentum of the cannon ball is zero.
d)the momentum of the cannon is equal to the magnitude of the momentum of the cannon ball and points in the same direction.

b)the momentum of the cannon is equal to the magnitude of the momentum of the cannon ball and points in the opposite direction.

Which has the greater momentum when moving?
a)bullet
b)a container ship
c)either of these depending on speed

c)either of these depending on speed

When Peter tosses an egg against a sagging sheet, the egg doesn’t break due to
a)reduced momentum.
b)reduced impulse.
c)both of these
d)neither of these

d)neither of these

A bungee jumper attains a speed of 30 m/s just as the bungee cord begins to stretch. If the period of stretch is 2 s while coming to a halt, the jumper’s average deceleration is about
a)g.
b)2 g.
c)1.5 g.
d)0.5 g.

c)1.5 g.

The force that accelerates a rocket in outer space is exerted on the rocket by the
a)exhaust gases.
b)atmospheric pressure.
c)rocket’s nose cone.
d)rocket’s wings.
e)none of the above

a)exhaust gases.

As Bronco Brown steps off a hovering high-flying helicopter and falls through the air, he experiences
a)an impulse.
b)an increasing speed.
c)a decreasing acceleration.
d)all of the above

d)all of the above

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

If a monkey floating in outer space throws his hat away, the hat and the monkey will both
a)move away from each other at the same speed.
b)move away from each other, but at different speeds.
c)come to a stop after a few minutes.
d)move a short distance and then go faster.
e)move a short distance and then slow down.

b)move away from each other, but at different speeds.

An open freight car rolls friction free along a horizontal track in a pouring rain that falls vertically. As water accumulates in the car, the car’s speed
a)increases.
b)doesn’t change.
c)decreases.
d)need more information

c)decreases.

A 2-kg rifle that is suspended by strings fires a 0.01-kg bullet at 200 m/s. The recoil velocity of the rifle is about
a)1 m/s.
b)0.1 m/s.
c)0.001 m/s.
d)0.01 m/s.
e)none of these

a)1 m/s.

A 5-kg shark swimming at 1 m/s swallows an absent-minded 1-kg fish swimming toward it at 4 m/s. The speed of the shark after his meal is
a)3/2 m/s.
b)1/5 m/s.
c)2/3 m/s.
d)1/6 m/s.
e)1/2 m/s.

d)1/6 m/s.

A sandbag motionless in outer space is hit by a three-times-as massive sandbag moving at 12 m/s. They stick together and move at a speed of
a)4 m/s.
b)3 m/s.
c)6 m/s.
d)8 m/s.
e)none of the above

e)none of the above