question

Which has a greater momentum: a heavy truck at rest or a moving skateboard?

answer

Moving skateboard

question

A slowly moving ship can have a greater momentum than a fast-moving racing car when _______.

answer

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

question

Distinguish between force and impulse.

answer

Impulse is force times a time interval.

question

An impulse can be increased by

answer

increasing the force or increasing the time interval.

question

The quantity that is called impulse can be measured by the _______.

answer

product of force and time.

question

How is the impulse -momentum relationship related to Newton's second law?

answer

F=ma=mÎ”v/Î”t, so Ft=Î”(mv)

question

To impart the greatest momentum to an object, you must

answer

exert the greatest force over the longest time.

question

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?

answer

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

question

Why is a force that is applied for a short time more effective in karate?

answer

The average force is increased.

question

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?

answer

Yes, always

question

What does it mean to say that momentum is conserved?

answer

It means momentum does not change.

question

When two vehicles collide, momentum is conserved _______.

answer

whether the collision is elastic or inelastic.

question

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

answer

remains the same

question

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

answer

Momentum is conserved in elastic and inelastic collisions.

question

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?

answer

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

question

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?

answer

Their speed is half the initial speed of car A.

question

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

answer

vectorally add up to equal the initial momentum of the firecracker

question

What is the momentum of an 8.4-kg bowling ball rolling at 1.0m/s ?
{Momentum = mv}

answer

p = 8.4 (kgâ‹…m)/s

question

What impulse occurs when an average force of 12N is exerted on a cart for 2.1s ?
[Impulse = Ft]

answer

p = 25 (kgâ‹…m)/s

question

What is the magnitude of the impulse on an 7.6-kg ball rolling at 1.4m/s when it bumps into a pillow and stops?
[Impulse = change in momentum: Ft=Î”mv]

answer

impulse = 11 Nâ‹…s

question

A 4.2-kg fish swimming 1.4m/s swallows an absentminded 1.0-kg fish swimming toward it at a speed that brings both fish to a halt immediately after lunch. Find the speed of the approaching smaller fish before lunch.

answer

v = 5.9 m/s

question

Two automobiles, each of mass 1100kg , are moving at the same speed, 23m/s , when they collide and stick together. In what direction and at what speed does the wreckage move if one car was driving north and one south.

answer

The wreckage after collision is motionless.

question

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

answer

momentum

question

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

answer

3 m/s

question

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

answer

less momentum

question

The total momentum of a flock of identical birds could be zero only if the birds are

answer

flying in different directions.

question

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

answer

3,000 kg m/s.

question

It is correct to say that impulse is equal to

answer

a corresponding change in momentum.

question

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

answer

lengthened time of contact.

question

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

answer

stopping time is longer on the carpet.

question

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

answer

Longer time

question

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

answer

greater with the brick wall

question

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

answer

both the same

question

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

answer

the target would be safer than the shooter.

question

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

answer

cannon has much more mass than the cannonball.

question

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

answer

greater

question

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

answer

friction between his feet and the board.

question

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?

answer

both the same

question

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

answer

move in the opposite direction at a lower speed.

question

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

answer

Earth would spin a bit slower.

question

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

answer

2 m/s.

question

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?

answer

6 m/s

question

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?

answer

all the same

question

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

answer

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

question

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

answer

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

question

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

answer

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

question

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

answer

both of these