Physics Chapter 6

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

0.5 m/s.

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

1 kg m/s.

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

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

1/6 m/s.

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

16 kg.

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

2/3 m/s.

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

2000 N.

The speed of a 4-kg ball with a momentum of 12 kg m/s is

3 m/s.

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

3,000 kg 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?

6 m/s

In which is momentum conserved: an elastic collision or an inelastic collision?

Momentum is conserved in elastic and inelastic collisions.

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?

The speed of car B is equal to the initial speed of A. (since the cars have the same mass they will have the same velocity)

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?

Their speed is half the initial speed of car A.

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?

Yes, always.

It is correct to say that impulse is equal to

a corresponding change in momentum.

As Bronco Brown steps off a hovering high-flying helicopter and falls through the air, he experiences

a decreasing acceleration. an increasing speed. an impulse. all of the above

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

a pickup truck speeding along a highway

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

about 1/10 as great.

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

acceleration

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?

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

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

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

both the same

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?

both the same

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

cannon has much more mass than the cannonball.

A cannonball following a parabolic path explodes into fragments. The momentum of the fragments

continue along the path as if the explosion didn't occur.

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

decreases

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

decreases.

Which has the greater momentum when moving?

either of these depending on speed *a container ship *a bullet

When a cannonball is fired from a cannon, the momentum of the recoiling cannon is momentarily _______.

equal and opposite to the momentum of the fired cannonball.

Freddy Frog drops vertically from a tree onto a horizontally-moving skateboard. The reason he doesn't slip off the skateboard is due to

friction between his feet and the board.

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

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

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

greater with the brick wall.

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

greater.

What is the magnitude of the impulse on an 7.4-kg ball rolling at 3.0 m/s when it bumps into a pillow and stops?

impulse = 22 N⋅s

When a vertically falling firecracker bursts, the vector sum of momentum fragments

in the vertical direction equals the momentum of the firecracker before bursting. in the horizontal direction cancels to zero. both of these

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

lengthened time of contact.

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

longer time.

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

momentum.

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

move away from each other, but at different speeds.

An astronaut floating alone in outer space throws a baseball. If the ball moves away at 20 m/s, the astronaut will

move in the opposite direction at a lower speed.

When a big fish swims into an oncoming smaller fish and swallows it, the momentum of the two-fish system _______.

remains the same.

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

stopping time is longer on the carpet.

A tiny gun made of a strong but very light material fires a bullet more massive than the gun itself. For such a weapon

the target would be safer than the shooter.

When a cue ball strikes an 8 ball head-on in a game of pool, the cue ball _______.

transfers its momentum to the 8 ball.

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

twice

When a falling firecracker explodes, the momenta of its pieces _______.

vectorally add up to equal the initial momentum of the firecracker

When two vehicles collide, momentum is conserved _______.

whether the collision is elastic or inelastic.

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

zero