Deck 6: Momentum

Question 1

To catch a fast-moving ball, you extend your hand forward before contact with the ball and let it ride backward in the direction of the ball's motion. Doing this reduces the force of contact on your hand principally because the

A)force of contact is reduced.
B)relative velocity is less.
C)time of contact is increased.
D)time of contact is decreased.
E)none of the above

Answer 1

time of contact is increased.

Question 2

Which has the greater momentum when moving?

A)a container ship
B)a bullet
C)either of these depending on speed

Answer 2

either of these depending on speed

Question 3

A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is

A)zero.
B)twice.
C)four times as much.
D)unchanged.

Answer 3

twice.

Question 4

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

Question 5

If several balls are thrown straight up with different initial speeds, the quantity that will have the same value along their paths is their

A)initial momentum.
B)maximum height.
C)time of travel.
D)acceleration.
E)none of the above

Question 6

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)12 m/s.
D)48 m/s.
E)none of the above

Question 7

Padded dashboards in cars are safer in an accident than non-padded ones because passengers hitting the dashboard encounter

A)lengthened time of contact.
B)shorter time of contact.
C)decreased impulse.
D)increased momentum.

Question 8

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

Question 9

Compared with falling on a stone floor, a wine glass may not break when it falls on a carpeted floor because the

A)carpeted floor provides a smaller impulse.
B)stopping time is shorter on the carpet.
C)stopping time is longer on the carpet.
D)carpet provides a smaller impulse and a longer time.

Question 10

When Peter tosses an egg against a sagging sheet, the egg doesn't break due to

A)reduced impulse.
B)reduced momentum.
C)both of these
D)neither of these

Question 11

The force on a dropped apple hitting the ground depends upon

A)the speed of the apple just before it hits.
B)the time of contact with the ground.
C)whether or not the apple bounces.
D)all of the above

Question 12

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)about the same momentum.
C)more momentum.

Question 13

A car traveling along the highway brakes to a stop over a certain distance. More braking force is required if the car has

A)more mass.
B)more momentum.
C)less stopping distance.
D)all of the above
E)none of the above

Question 14

The impulse-momentum relationship is a direct result of

A)Newton's 1st law.
B)Newton's 2nd law.
C)Newton's 3rd law.
D)Newton's law of gravity.

Question 15

The mass of a ball moving at 3 m/s with a momentum of 48 kg m/s is

A)4 kg.
B)12 kg.
C)16 kg.
D)144 kg.
E)none of these

Question 16

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/.

Question 17

Which of the following has the largest momentum relative to Earth's surface?

A)a tightrope walker crossing Niagara Falls
B)a pickup truck speeding along a highway
C)a Mack truck parked in a parking lot
D)the Science building on campus
E)a mouse running across your room

Question 18

When you jump from an elevated position you usually bend your knees upon reaching the ground, which makes the time of the contact about 10 times that of a stiff-legged landing. In this way the average force your body experiences is

A)less than 1/10 as great.
B)more than 1/10 as great.
C)about 1/10 as great.
D)about 10 times as great.

Question 19

It is correct to say that impulse is equal to

A)momentum.
B)a corresponding change in momentum.
C)force multiplied by the distance it acts.
D)velocity multiplied by time.

Question 20

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 the same direction.
C)flying in different directions.
D)very tired and coming down to rest.

Question 21

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)0.5 g.
B)g.
C)1.5 g.
D)2 g.

Question 22

When a boxer is moving away from a punch, the force experienced is reduced because

A)momentum transfer is reduced.
B)the time of contact is increased.
C)the force is less effective.
D)all of the above

Question 23

Whether a truck comes to a stop by crashing into a haystack or a brick wall, the impulse is

A)greater with the haystack.
B)greater with the brick wall.
C)both the same

Question 24

When a boxer moves into an oncoming punch, the force experienced is

A)decreased.
B)increased.
C)no different, but the timing is different.
D)all of the above

Question 25

A falling 1-N apple hits the ground with a force of about

A)1 N.
B)2 N.
C)4 N.
D)10 N.
E)need more information

Question 26

Which produces more force: driving into a very massive concrete wall with no "give," or having a head-on collision with an identical car moving toward you at the same speed?

A)car
B)wall
C)both the same
D)need more information

Question 27

Whether a truck comes to a stop by crashing into a haystack or a brick wall, the stopping force is

A)greater with the haystack.
B)greater with the brick wall.
C)both the same

Question 28

A karate expert executes a swift blow and breaks a cement block with her bare hand. The magnitude of the force on her hand is

A)zero.
B)less than the force applied to the cement block.
C)the same as the force applied to the block.
D)more than the force applied to the block.
E)need more information

Question 29

The greater efficiency achieved with the curved blades of a Pelton wheel is due to

A)bouncing.
B)greater time of water impact.
C)rotational momentum.
D)divided impulse.

Question 30

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)smaller.
C)the same.

Question 31

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

Question 32

A piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. Both move with a combined momentum of

A)less than 1 unit.
B)more than 1 unit.
C)1 unit.
D)need more information

Question 33

The average braking force of a 1000-kg car moving at 10 m/s braking to a stop in 5 s is

A)1000 N.
B)2000 N.
C)3000 N.
D)4000 N.
E)5000 N.

Question 34

A softer landing occurs when an falling object bounces from a surface

A)in a extended time.
B)quickly.
C)either of these
D)neither of these

Question 35

The force that accelerates a rocket in outer space is exerted on the rocket by the

A)rocket's nose cone.
B)rocket's wings.
C)atmospheric pressure.
D)exhaust gases.
E)none of the above

Question 36

A karate chop is more effective if one's hand

A)follows through upon impact.
B)bounces upon impact.
C)extends the time upon impact.

Question 37

The conservation of momentum is most closely related to

A)Newton's 1st law.
B)Newton's 2nd law.
C)Newton's 3rd law.
D)Newton's law of gravity

Question 38

The change in momentum that occurs when a 1.0 kg ball traveling at 4.0 m/s strikes a wall and bounces back at 2.0 m/s is

A)2 kg m/s.
B)4 kg m/s.
C)6 kg m/s.
D)8 kg m/s.

Question 39

A cannon recoils while firing a cannonball. The speed of the cannon's recoil is relatively small because the

A)force against the cannon is smaller than against the ball.
B)momentum is mainly concentrated in the cannonball.
C)cannon has much more mass than the cannonball.
D)momentum of the cannon is smaller.

Question 40

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)the target would be safer than the shooter.
B)recoil problems would be lessened.
C)conservation of energy would not hold.
D)conservation of momentum would not hold.
E)both conservation of energy and momentum would not hold.

Question 41

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)the bug
B)your car
C)both the same

Question 42

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)4 m/s
B)5 m/s
C)6 m/s
D)8 m/s
E)none of the above

Question 43

A fan attached to an ice sailcraft stalled on a windless day blows air into the sail that bounces backward upon impact. The boat

A)moves in the direction of the wind impact force.
B)does not move by this wind impact.
C)moves, but in the opposite direction of the wind impact force.

Question 44

When bullets are fired from an airplane in the forward direction, the momentum of the airplane is

A)decreased.
B)unchanged.
C)increased.

Question 45

Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet?

A)zero
B)half the sum of their original momentums
C)twice the sum of their original momentums
D)need more information

Question 46

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.
D)none of the above

Question 47

A golf ball moving forward with 1 unit of momentum strikes and bounces backward off a heavy bowling ball that is initially at rest and free to move. The bowling ball is set in motion with a momentum of

A)less than 1 unit.
B)more than 1 unit.
C)1 unit.
D)not enough information

Question 48

If a monkey floating in outer space throws his hat away, the hat and the monkey will both

A)move away from each other, but at different speeds.
B)move away from each other at the same speed.
C)move a short distance and then slow down.
D)move a short distance and then go faster.
E)come to a stop after a few minutes.

Question 49

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)decreases.
C)doesn't change.
D)need more information

Question 50

If all people, animals, trains and trucks all over the world began to walk or run towards the east (opposite the direction of Earth's spin), then

A)Earth would spin a bit faster.
B)Earth would spin a bit slower.
C)Earth's spin would not be affected at all.

Question 51

A 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5-kg bowling ball initially at rest. The bowling ball and putty then move with a momentum of

A)0 kg m/s.
B)1 kg m/s.
C)2 kg m/s.
D)5 kg m/s.
E)more than 5 kg m/s.

Question 52

When Freddy Frog drops vertically from a tree onto a horizontally-moving skateboard, the speed of the skateboard

A)decreases.
B)increases.
C)neither decreases nor increases.

Question 53

A 5-kg fish swimming at 1 m/s swallows an absent-minded 1-kg fish at rest. The speed of the larger fish after lunch is

A)1/2 m/s.
B)2/5 m/s.
C)5/6 m/s.
D)6/5 m/s.
E)1 m/s.

Question 54

Consider massive gliders that slide friction-free along a horizontal air track. Glider A has a mass of 1 kg, a speed of 1 m/s, and collides with Glider B that has a mass of 5 kg and is at rest. If they stick upon collision, their speed after collision will be

A)1/4 m/s.
B)1/5 m/s.
C)1/6 m/s.
D)1 m/s.
E)none of the above

Question 55

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.

Question 56

Recoil is noticeable if we throw a heavy ball while standing on roller skates. If instead we go through the motions of throwing the ball but hold onto it, our net recoil will be

A)zero.
B)the same as before.
C)small, but noticeable.

Question 57

Two identical gliders slide toward each other on an air track. One moves at 1 m/s and the other at 2 m/s. They collide, stick, and moves at

A)1/2 m/s.
B)1/3 m/s.
C)1/6 m/s.
D)3/4 m/s.
E)1.5 m/s.

Question 58

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 m/s.
B)1 m/s.
C)2/3 m/s.
D)1/3 m/s.

Question 59

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)1/2 m/s.
B)1/5 m/s.
C)1/6 m/s.
D)2/3 m/s.
E)3/2 m/s.

Question 60

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)0.001 m/s.
B)0.01 m/s.
C)0.1 m/s.
D)1 m/s.
E)none of these

Question 61

A firecracker bursts while freely falling. The combined momentum of its fragments

A)equals the momentum of the firecracker at the time of burst
B)cancels to the firecracker's momentum at the time of bursting.
C)cancels to zero.
D)none of the above

Question 62

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)parallel to either of the cars before collision.
B)at 45 degrees to the direction of either car before collision.
C)at some angle other than 45 degrees.

Question 63

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)the same as the magnitude of momentum of either car before collision.
B)less than 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

Question 64

Two identical freight cars roll without friction (one at 1 m/s, the other at 2 m/s)toward each other on a level track. They collide, couple together, and roll away in the direction of

A)the slower car.
B)the faster car.
C)neither, for they stop.

Question 65

A 1-kg glider and a 2-kg glider both slide toward each other at 1 m/s on an air track. They collide and stick. The combined mass moves at

A)0 m/s.
B)1/2 m/s.
C)1/3 m/s.
D)1/6 m/s.
E)1.5 m/s.

Question 66

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)3 m/s.
B)4 m/s.
C)6 m/s.
D)8 m/s.
E)none of the above

Question 67

Two 5000-kg rail cars roll without friction (one at 1 m/s, the other at 2 m/s)toward each other on a level track. They collide, couple, and roll together with a combined momentum of

A)zero.
B)5000 kg m/s.
C)10,000 kg m/s.
D)15,000 kg m/s.

Question 68

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

Question 69

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)blue car
C)green car
D)all the same

Question 70

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

Question 71

Two identical objects in outer space, one moving at 2 m/s, the other at 1 m/s, have a head-on collision and stick together. Their combined speed after the collision is

A)0.5 m/s.
B)0.33 m/s.
C)0.67 m/s.
D)1.0 m/s.
E)none of the above