PY 131 Chapter 6 Conceptual Academy

A slow moving object can have a lot of momentum if is also has

mass

If you are sitting still on Earth, then your momentum is

large because of the motion of Earth around the Sun.

Impulse is the product of

time and force.

A raw egg will not break when tossed into a hanging bed sheet because

the time of impact is long.

In this lesson we derive the impulse-momentum relationship by way of

**Response**

Newton's second law.

In this lesson we stated that how much momentum is changed depends on how much

impulse is applied.

When the impulse on an object is zero

no change in momentum occurs.

When an object bounces, the change in momentum is

double

A flower pot falls on your head. Would it be better if it breaks or bounces?

Breaks.

The conservation of momentum is most akin to

Newton's third law.

Ideally, when a cannon is fired, momentum is gained by

the cannon and cannonball in equal amounts.

Colliding billiard balls nicely illustrate

elastic collisions

The two-fish collision nicely illustrates an

inelastic collision.

When the momentum of an object is calculated to be negative in a collision, it means

a reversal of direction.

Before lunch, the two-fish system has a certain momentum. After lunch the momentum of the system is

the same.

One reason for the slowing of the skateboard when Freddy lands on it involves

friction between Freddy's feet and the skateboard

Before Freddy lands on the skateboard it has a certain momentum. After landing, the skateboard's momentum

remains the same.

What changes when Freddy rides the skateboard is

speed.

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

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

The quantity that is called impulse can be measured by the

product of force and time.

Follow through is important in golf because it results in a greater

impulse on the ball.

A boxer rides with the punch so as to reduce

force

Cassy can get more force on the bricks she breaks with a blow of her bare hand when

her hand is made to bounce from the bricks.

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.

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.

When two vehicles collide, momentum is conserved

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

remains the same.

When a falling firecracker explodes, the momenta of its pieces

vectorally add to equal the initial momentum of the firecracker.

A fully loaded truck and a small go-cart roll down the same hill using no brakes. Assuming no friction in both, at the hill's bottom, the go-cart will have more

momentum?

Consider a small gun made of a strong but light weight plastic. If the gun's mass were less than that of the bullet, then

the target would be safer than the shooter.

A 1 kg fish not thinking very clearly swims a 4 m/s toward a 5 kg shark approaching a 1 /4. Just after lunch, the shark is moving at about

1/6 m/s

A bullet's speed will match the gun's recoil speed

if the mass of the bullet equals the mass of the gun.

If every moving animal, truck, train and boat began moving in unison toward the west, then

Earth would spin a bit faster

A bicycle is gliding at 3 m/s. Its momentum is 48 kg m/s. The mass of the bicycle is

16 kg

The force experienced by a dropped apple as it hits the floor depends upon

All of these

You'll recoil backward if you throw a heavy rock forward while standing on roller skates. If you threw the rock forward, but then held onto it at the last moment, your recoil would be

zero

A 5 kg skate board has a momentum of 15 kg m/s. The speed of the skateboard is

3 m/s

Consider a horizontal friction free air track with two gliders each moving at 1 m/s and toward each other. One glider has a mass of 1 kg, while the other has a mass of 2 kg. Upon sticking together as a single mass, their speed will be

1/3 m/s

A 1 kg fish is sleeping at rest when it gets swallowed by a larger 5 kg fish moving toward it at 1 m/s. After lunch, the larger fish is moving at about

5/6 m/s

(bigger fish is 5x bigger than little fish. Or little fish is 1/5 the size of the big fish. When the big fish swallows the little fish, it is now 6kg and isn’t moving at the same momentum--1 m/s--so it has to be just a little under, at 5/6)

The relationship between impulse and momentum is a direct consequence of

Newtons 2nd law

A large fan is attached to the back of a sail craft on ice skates on a frozen pond on a day with no wind. The fan blows forward to the sail into which air hits and bounces backward. The craft can

then move forward

A change in momentum (mv) = Ft. According to this equation, a person is not hurt as much when falling on a carpeted floor that "gives way". The letter F corresponds to the force acting on

either person or on the floor

Bending your knees upon jumping to the ground lengthens the duration of impact by about 10 times making the average force on your body

about 1/10 as great.

Consider a horizontal friction free air track with two identical gliders each moving toward each other. One glider moves at 1 m/s while the other at 2 m/s. Upon colliding they stick together and move at

1/2 m/s

An orange falls to the ground and in doing so transfers to the ground an amount of momentum that is

**greater than that of the orange only if the orange bounces.**

Consider a horizontal friction free air track with two gliders. The 1 kg Glider X glides at 1 m/s colliding with the 5 kg Glider Y, which is initially at rest. Assuming they stick together upon colliding, their speed will then be

1/6 m/s

A quickly moving oject is heading toward you. To slow it down you want to apply the smallest force possible so that you're not hurt. Accordingly, you lower its momentum over a

long time

To stop a traveling car within a certain distance requires a certain force. But more force will be required if the car has

All of the these, more momentum, less stopping distance, more mass.

In deep space, a sticky wad of bubble gum moves with a momentum of one unit. It hits and sticks to a large bowling ball at relative rest with zero momentum. Together, the gum and bowling ball then travel with a total momentum of

1 unit

With bare hand, a karate black belt swiftly breaks a block of cement. The strength of the force on on her hand is

identical to the force applied to the block.

A bungee jumper reaches a speed of 40 m/s just as the cord begins to stretch. If the time of stretch is 4 s, what is the magnitude of the jumper's average deceleration?

1\.0 g

A bug splats into the windshield of a car speeding down a road. Upon impact, the change in momentum is greater on the

Both the same

As a baseball player catches a ball, her hand rides backward with the ball as it lands in the glove. This minimizes impact because the

time of impact is increased

A truck of 1000 kg has a speed of 10 m/s. The brakes are applied and the truck stops in 5 seconds. The force of braking (on average) is

2000 N

A 1000 kg truck traveling at 10 m/s comes to a complete stop in 5 seconds. The force of braking (on average) must be

2000 N

A freight train car of 5000 kg traveling at 2 m/s bumps into a 10,000 kg freight train car at rest. After coupling, they travel together at a speed of

2/3 m/s

A padded automobile dashboard is safer than a non-padded dashboard because some one in the car hitting the it has

increased time of impact

A 1 N orange falls and hits the ground. The force of impact is about

not enough information is provided.

With the same speed and mass 2 billiard balls roll straight toward each other. Upon meeting their combined momentum is

zero

Floating in deep space, a robot throws away one of its dead batteries. The robot and the battery will both

move away from each other, but at different speeds.

A light go-cart and a heavy car roll down the same hill at the same speed. A force is applied to each to bring them to a stop in the same span of time. The force applied to the car must be

greater

A cannon ball is shot from a short barrel. If instead it were shot from a longer barrel, the speed at which it leaves the barrel would be

more

Momentum conservation is deeply connected to

Newton’s 3rd Law

In deep space a 1 kg glob of sticky gum gliding at 1 m/s collides head-on with a 5 kg rock at relative rest. After the collision, the gum is moving at

1/6 m/s

Deep in outer space a 3 kg sand bag moving at 12 m/s collides head on and sticks to a 1 kg sand bag with no relative motion. After the collision, these two sand bags travel at a speed of

None of these

In deep space, a 1 kg sticky wad of bubble gum moving at 1 m/s hits and sticks to a 5 kg brick at relative rest with zero momentum. Together, the gum and brick then travel with a total momentum of

1 kg/m/s

A 2 kg rifle is suspended horizontally by strings. It fires a 0.01 kg bullet at 200 m/s. The rifle recoils backward with a speed of about

1 m/s

In deep space, a golf ball with two units of momentum hits and bounces directly backward off of a massive bowling ball initially at rest. The bowling ball then has a momentum of

more than two units

Consider what makes for great momentum. Then select which of the following has the greatest momentum relative to the surface of planet Earth.

A pickup truck speeding along a highway.

Identical geese in a flock can have a total momentum of zero only if the geese are

flying in different directions

When a rifle fires a bullet the speed of recoil is minimal because the

rifle has much more mass than the bullet.

Two tennis balls are dropped at the same time from a tall tower. One is filled with sand, which means it hits the ground with greater

momentum

A fragile glass vase hitting a carpet versus a stone floor might not shatter because the

stopping time is longer on the carpet.

A freight train car of 5000 kg bumps into a 10,000 kg freight train car at rest. After coupling they travel together at 2 m/s. The 5000 kg car, therefore, had an initial speed of

6 m/s

A force is needed to bring a light car to a full stop. This force is (less than, more than, the same as) that needed to bring a massive truck also to a full stop.

More information is required.

Consider at 1 kg ball hitting a wall at 4 m/s and bouncing back at 2 m/s. The change in momentum of this ball is

6 kg m/s.

By definition, impulse is

the change in momentum it produces.

Car 1 and Car 2 have the same momentum just before crashing together head-on. Car 3 with the same momentum crashes head-on into an enormous cement wall. Experiencing the greatest impulse is

All will receive the same impulse.

Floating in space, an astronaut throws an orange releasing it at 20 m/s. The astronaut then moves in the opposite direction

but at a slower speed.

A rolling freight train has much momentum. At the same speed but twice the mass its momentum

is doubled

Which produces more force on your car: Crashing into a brick building or crashing head-on into another car completely identical and driving at the same speed?

Both the same

A rocket in outer space is accelerated by a net force, which is applied to the rocket by the

exhaust gases.