Physics Final Coureskey Answers

An electron is shot at two small holes that are close together. What happens?

The electron goes through both holes simultaneously

True or False: Atmospheric pressure is due to gravity

True

True or False: Energy is always conserved

True

True or false: Simple harmonic motion is described by a sinusoidal function.

True

True or false: The astronauts inside the International Space Station are in free fall.

True

A roller coaster starts from a hill of height h, rolls down and then does a loop-the-loop of radius R. Ignore friction and air resistance. What is the minimum height h that will work, such that unbuckled passengers won't fall out?

2.5R

A block of mass m oscillates on a horizontal spring with period T = 2.0 s. If a second identical block is glued to the top of the first block, the new period will be...

2.8 s

Kinetic energy is...

1/2 mass x speed^2

What's the longest (vertical) straw superman can drink through?

10 m

A car of mass 1000 kg is moving at 20 m/s. It hits a stopped car of mass 1000 kg and the two cars stick together and move forward. What is the speed of the two cars?

10 m/s

A golf ball of mass 50 grams is struck with a club. The ball, initially at rest, leaves the club at 100 m/s. If the club is in contact with the golf ball for 5 ms, what is the average foce on the ball?

1000 N

A mass oscillates on a horizontal spring with period T = 2.0 s. If the amplitude of the oscillation is doubled, the new period will be...

2.0 s

A superball of mass m = 10 grams is thrown at a wall at v = 20 m/s. It rebounds off the wall at the same speed, and it is in contact with the wall for 10 ms. What is the average force exerted by the wall on the ball?

40 N

You are riding in a roller coaster and it does a loop-the-loop. What is the minimum speed the roller coaster can have at the top of the loop such that unbuckled passengers will not fall out? Let the radius of the loop R = 10 meters.

9.9 m/s

How much of an iceberg is underwater?

90%

You are driving in your car at 50 mph and you run into a brick wall. A year later (and with a new car), you are driving down the freeway at 50 mph and you have a head-on collision with another (identical) car coming the other way also at 50 mph. Which accident does more damage to your car?

Both the same

What term is used to describe an oscillator that "runs down" and eventually stops?

Damped oscillator.

If I throw an object up in the air, what is its acceleration at the top of its motion?

Downwards

A light plastic cart (m1 = 4 kg) and a heavy steel cart (m2 = 16 kg) are both pushed with the same force of 10 N for a distance of 1.0 m, starting from rest. After the force is removed, the kinetic energy of the light plastic cart is ________ that of the heavy steel cart.

Equal to

True or False: A suction cup works in outer space.

False

True or False: Kinetic energy is always conserved

False

You are floating in a pool on a raft filled with bricks. You throw the bricks into the pool and they sink to the bottom. What happens to the water level in the pool?

It goes down

When I throw a ball up in the air, the ball rises, comes to a stop, and then falls. What can you say about its energy? (Ignore air resistance.)

Kinetic energy transforms to potential energy and then back to kinetic energy.

Two blocks are of identical size. One is made of lead and sits on the bottom of a pond; the other is of wood and floats on top. Upon which is the buoyant force greater?

Lead block

When an object is in equilibrium, which of the following is true?

Net force and net torque equal zero.

A ball falls from the top of a building. Does the ball conserve momentum?

No

A perfectly elastic collision is a collision...

That conserves mechanical energy.

The suspension system in your car is a damped oscillator. The springs provide the bounce. What provides the damping?

The Shocks

Impulse is...

The area under the force curve in a force-versus-time graph.

You are riding a roller coaster and it does a loop-the-loop. Which part of the ride do you feel heaviest?

The bottom of the loop.

Two cars collide at right angles and stick together. One is traveling East and the other is traveling North. If after the collision the angle of their velocities is 45 degrees North of East, this means before the collision:

The magnitudes of the momenta of the cars were equal.

Moment of inertia is...

The rotational equivalent of mass.

The total momentum of a system is conserved if...

The system is isolated

A piece of glass is broken into two pieces of different size. How do their densities compare?

Their densities are equal.

Two bungee jumpers hold onto each other and jump off a bridge. The stretched bungee just reaches a river below, and at this point, one of the bungee jumpers is released into the water. What happens to the other jumper?

They fly back up halfway to the bridge.

A skier is gliding down a slope at a constant speed. What energy transformation is taking place?

Ug → Eth

You are driving your car in a circle at constant speed. Are you accelerating?

Yes

While doing the bench press, you push a mass m up to a height h, then let it back down to where it started. How much work have you done?

Zero

The speed of light c= 3*10^8 m/s. Pretend you are driving your car at 90% the speed of light (0.9c). Coming the other way on the freeway is a car moving the opposite direction at 0.9c. If you measure the speed of the light emitted by their headlights, what do you get?

c

Two coins rotate on a turntable. Coin B is twice as far from the axis as coin A. The angular velocity of A is...

equal to that of B.

A car is moving in a circle at constant speed. How much work is done by the static friction between the tires and the road?

force of kinetic friction * velocity

In the absence of friction, a spinning top will continue to spin...

forever

A light plastic cart and a heavy steel cart are both pushed with the same force for 1.0 seconds, starting from rest. After the force is removed, the momentum of the light plastic car is ____________ that of the heavy steel cart.

less than

A block oscillates on a vertical spring. When the block is at the lowest point of the oscillation, it's acceleration is...

zero.