Physics Exam 2

A skier starts from rest at the top of each of the hills shown in the figure. On which hill will the skier have the highest speed at the bottom assuming a small amount of friction:

the tallest hills, no matter how steep

A small car and a heavy pickup truck are both out of gas. The truck has twice the mass of the car. After you push both the car and the truck for the same distance with the same force, what can you say about the momentum and kinetic energy of the car and the truck? Ignore friction.

they have the same kinetic energy but the truck has more momentum than the car

A small car and a heavy pickup truck are both out of gas. The truck has twice the mass of the car. After you push both the car and the truck for the same amount of time with the same force, what can you say about the momentum and kinetic energy of the car and the truck? Ignore friction.

they have the same momentum, but the car has more kinetic energy than the truck

An astronaut is a short distance away from her space station without a tether rope. She has a large wrench. What should she do with the wrench to move toward the space station?

throw it directly away from the space station

In a rotating vertical cylinder (Rotor-ride) a rider finds herself pressed with her back to the rotating wall.(Figure 1) Which is the correct free body diagram?

towards the center, up, and down

The solid dot shown in the figure below is a pivot point. The board can rotate about the pivot. Which force shown exerts the largest magnitude torque on the board?

(c)

An object at rest begins to rotate with a constant angular acceleration.If this object rotates through an angle θ in time t, through what angle did it rotate in the time 12t?If this object rotates through an angle in time , through what angle did it rotate in the time ?

1/4 theta

A car accelerates from rest to 30 km/h. Later, on a highway it accelerates from 30 km/h to 60 km/h. Which takes more energy: going from 0 to 30 or from 30 to 60?

30 to 60

When the speed of your car is doubled, by what factor does its kinetic energy increase?

4

A traveling car at velocity v can stop in a minimum distance d. What would be the car's minimum stopping distance if it were traveling at a velocity of 2v?

4d

Which of the following point towards the center of the circle in uniform circular motion?

Acceleration, net force.

Two balls are thrown off a building with the same speed, one straight up and one at a 45 ∘ angle. Which statement is true if air resistance can be ignored?

Both hit the ground with the same speed

A car drives at steady speed around a perfectly circular track.

Both the acceleration and net force on the car point inward.

Which pulls harder gravitationally, the Earth on the Moon, or the Moon on the Earth? Which accelerates more?

Both the same; the Moon.

A ball is thrown straight up. At what point does the ball have the most energy? Ignore air resistance.

Everywhere. The energy of the ball is the same at all of these points.

A bowling ball is dropped from a height h onto the center of a trampoline, which launches the ball back up into the air. How high will the ball rise?

No more than h - probably a little less.

A satellite in circular orbit around the Earth moves at constant speed. This orbit is maintained by the force of gravity between the Earth and the satellite, yet no work is done on the satellite. How is this possible?

No work is done if the direction of motion is perpendicular to the force.

A Ping-Pong ball is shot into a circular tube that is lying flat (horizontal) on a table-top. When the Ping-Pong ball exits the tube, which path will it follow in the figure?

Straight out, follows velocity vector

A bowling ball hangs from a 1 m long cord.i) a 200 gram putty ball moving 5 m/s hits the bowling ball and sticks to it, causing the bowling ball to swing up ii) 200 gram rubber ball moving 5 m/s hits the bowling ball and bounces straight back up at nearly 5 m/s causing the bowling ball to swing up. Describe what happens.

The ball swings farther up in (ii) than in (i)

A baseball is pitched horizontally toward home plate with a velocity of 110 km/h.In which of the following scenarios does the baseball have the largest change in momentum?

The baseball is hit straight back to the pitcher at a speed of 110 km/h.

While driving fast around a sharp right turn, you find yourself pressing against the car door. What is happening?

The door is exerting a rightward force on you.

A ball is thrown straight up. Neglecting air resistance, which statement is NOT true regarding the energy of the ball?

The potential energy decreases while the ball is going up.

Engines, including car engines, are rated in horsepower. What is horsepower?

The rate at which the engine can do work

Assuming that there is a small amount of friction on the hill which the skier skis, which hill will he have the highest speed at the bottom of?

The tallest hill with the steepest slope

Two satellites orbit the Earth in circular orbits of the same radius. One satellite is twice as massive as the other. Which statement is true about the speeds of these satellites?

The two satellites have the same speed.

A truck going 15 km/h has a head-on collision with a small car going 30 km/h. Which statement best describes the situation?

They both have the same change in magnitude of momentum because momentum is conserved

A child whirls a ball in a vertical circle. Assuming the speed of the ball is constant (an approximation) , when would the tension in the cord connected to the ball be greatest?

at the bottom of the circle.

A small boat coasts at constant speed under a bridge. A heavy sack of sand is dropped from the bridge onto the boat. The speed of the boat,

decreases

A penny is placed on a turntable which is spinning clockwise. If the power to the turntable is turned off, which arrow best represents the direction of the acceleration of the penny at point P while the turntable is still spinning but slowing down?

down and to the right

Bonnie sits on the outer rim of a merry-go-round, and Jill sits midway between the center and the rim. The merry-go-round makes one complete revolution every 2 seconds. Jill's linear velocity is:

half of Bonnies

The moon does not crash into the Earth because:

it is freely falling but it has a high tangential velocity.

A space shuttle in orbit around the Earth carries its payload with its mechanical arm. Suddenly, the arm malfunctions and releases the payload. What will happen to the payload?

it will remain in the same orbit with the shuttle

A man pushes a block up an incline at a constant speed. As the block moves up the incline,

its potential energy increases and its kinetic energy stays the same.

A railroad tank car contains milk and rolls at a constant speed along a level track. The milk begins to leak out the bottom. The car then,

maintains a constant speed

Two identical billiard balls traveling at the same speed have a head-on collision and rebound.If the balls had twice the mass, but maintained the same size and speed, how would the rebound be different?

no difference

You push very hard on a heavy desk, trying to move it. You do work on the desk:

one if it starts moving

The space shuttle, in circular orbit around the earth, collides with a small asteroid which ends up in the shuttle's storage bay. For this collision what is conserved?

only momentum is conserved

In the International Space Station which orbits Earth, astronauts experience apparent weightlessness because:

the astronauts and the station are in free fall towards the center of the Earth.

You push a heavy crate down a ramp at a constant velocity. Only four forces act on the crate. Which force does the greatest magnitude of work on the crate?

the force of friction

A golf ball and an equal-mass bean bag are dropped from the same height and hit the ground. The bean bag stays on the ground while the golf ball rebounds.Which experiences the greater impulse from the ground?

the golf ball

You are lying in bed and want to shut your bedroom door. You have a bouncy "superball" and a blob of clay, both with the same mass. Which one would be more effective to throw at your door to close it?

the superball

A car speedometer that is supposed to read the linear speed of the car uses a device that actually measures the angular speed of the tires.If larger-diameter tires are mounted on the car instead, how will that affect the speedometer reading?

will read low