PRACTICE EXAM #2

A rocket fired vertically at 11.2 km/s will escape the Earth. If it is instead fired horizontally at this speed, free from obstructions, will it still escape the Earth?

Yes

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 to the force that stops the car, the force needed to stop the truck is smaller.

greater

A boy plays solitary seesaw by placing a long plank over a small rock and sitting at one end of the plank. When the seesaw is balanced, the boy's mass is

greater than the mass of the seesaw

Centrifugal forces are an apparent reality to observers in a reference frame that is

rotating

Angular momentum is greater for a satellite when it is at the

same at apogee and perigee

A black hole is

simply the remains of a giant star that has undergone gravitational collapse

Which requires the most amount of work by the brakes of a car?

slowing down from 100 km/h to 70 km/h

Since each rolling wheel of a railroad train is tapered, the narrow part of the wheel has a tangential speed that is

smaller than that of the wide part

The force of gravity acting on you will increase if you

stand on a planet with a radius that is shrinking

For a system in mechanical equilibrium,

the resultant forces and torques must both be zero

Both A 50-kg sack is lifted 2 meters from the ground and a 25-kg sack is lifted 4 meters in the same time. The power expended in raising the 50-kg sack is

the same

If the sun collapsed to a black hole, the Earth's gravitational attraction to it would be

the same

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

0

A bullet fired horizontally over level ground hits the ground in 0.5 second. If it had been fired with twice the speed in the same direction, it would have hit the ground in _____ (ignore air drag)

0.5 s

An object is dropped and freely falls to the ground with an acceleration of 1 g. If it is thrown upward at an angle instead, its acceleration will be

1 g downward

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 piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. After the putty sticks to the ball, both move with a combined momentum of

1 unit

An airplane travels at 141 km/h toward the northeast. What is its component of velocity due north?

100 km/h

An airplane that flies at 100 km/h in a 100 km/h hurricane crosswind has a ground speed (relative to ground) of

141 km/h

A car moves 4 times as fast as another identical car. Compared to the slower car, the faster car has

16 times the KE

A car moving at 50 km/hr skids 20 m with locked brakes. How far will the car skid with locked brakes if it were traveling at 150 km/hr?

180 m

Do 100 J of work in 50 s and your power output is

2 W

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

2000 N

A 2500-N pile-driver ram (heavy weight) falls 10 m and drives a post 0.1 m into the ground. The average impact force on the ram is

250,000 N

A jack system will increase the potential energy of a heavy load by 1000 J with a work input of 2000 J. The efficiency of the jack system is

50%

What is the force of gravity on a 500-newton woman standing on the Earth's surface?

500 N

A bullet is fired horizontally with an initial velocity of 300 m/s from a tower 20 m high. If air resistance is negligible, the horizontal distance the bullet travels before hitting the ground is about

600 m

Suppose you're on a Ferris wheel at a carnival, seated 10 m from the Ferris wheel's axis. If you make a complete rotation each minute, your linear speed is

62.8 m/min

An object is placed exactly halfway between the Earth and moon. The object will fall toward the

Earth

The concept of force is not fundamental to _________ (that is, it is not needed to make the theory work)

Einstein's theory of gravitation

How far must one travel to get away from the Earth's gravitational field?

Forget it; you can't travel far enough

A pulley system raises a 1000-N load 2 meters with 100 N of input force. The efficiency of the system is

Not enough information is given

An astronaut, floating in space, throws a ball as massive as herself toward her nearby spaceship. If the ball bounces back toward her without losing speed, her best choice at that time is to...

Radio for help since she can't catch the ball

A flower pot of mass m falls from rest to the ground below, a distance h. Which statement is correct?

The KE of the pot when it hits the ground is proportional to h

A baseball bat is balanced on a fulcrum. The center of gravity of the bat is located

above the fulcrum

Consider a hydraulic press. It works just like a lever. When the input piston is depressed 20 cm, the output piston is raised 1 cm. On this same press, an input force of 1 N can lift a load of

all of these

The force on an apple hitting the ground depends upon...

all of these

A phonograph record player has constant rotational speed. The speed of the record surface relative to the pickup needle is greatest

at the beginning of the record

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 supplier wants to make a profit by buying gold (which is sold by weight) at one altitude and selling it at the same price per pound at another altitude. The supplier should

buy at a high altitude and sell at a low altitude

A coin and a ring roll down an incline starting at the same time. The one to reach the bottom first will be the

coin

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

According to Newton, doubling the distance between two interacting objects

divides by 4 the gravitational force between them

A tightrope walker more easily balances on a tightwire if his pole

droops

According to Kepler's laws, the paths of planets about the sun are

ellipses

The force of gravity does work on a satellite to change its speed. This happens when the satellite is in

elliptical orbit

The force that accelerates a rocket in outer space is exerted on the rocket by the

exhaust gases

Two identical arrows, one with twice the speed of the other, are fired into a hay bale. The faster arrow will penetrate

four times as far as the slower arrow

If a moon orbits one of our most distant planets in an elliptical path. The distance that the moon covers each day is

greatest when the moon is closest to the planet

An upright broom is easier to balance vertically when the heavier end is

highest, farthest from your hand

A bullet is fired from a gun. The speed of the bullet will be about the same as the speed of the recoiling gun

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

If the earth rotated slower about its axis, your apparent weight would

increase

Two objects move toward each other because of gravity. As the objects get closer and closer, the force between them

increases

When the distance between two stars decreases by half, the force between them

increases to four times as much

A projectile is fired horizontally in a region of no air resistance. The projectile maintains its horizontal component of velocity because

it is not acted on by any horizontal forces

Suppose the moon had twice as much mass as it now does and still orbited the Earth at the same distance. In that case, the ocean bulges on Earth would be

larger

When you are in the way of a fast-moving object and can't get out of its way, you will suffer a smaller force of impact if you decrease its momentum over a...

long time

If the speed of a moving object doubles, which of the following also doubles?

momentum

Two objects have the same size and shape, but one is much heavier than the other. When they are dropped simultaneously from a tower, they reach the ground at the same time, but the heavier one has a greater...

momentum

A golf ball moving forward with 1 unit of momentum strikes and bounces backward off a heavy bowling ball that is initially at rest and free to move. The bowling ball is set in motion with a momentum of

more than 1 unit

A lunar month is about 28 days. If the moon were farther from the Earth than it is now, the lunar month would be

more than 28 days

A satellite in an elliptical orbit travels at constant

none of these

If the sun somehow became twice as massive, your weight as normally measured here on earth would

not change

If your mass, the mass of the Earth, and the mass of everything in the solar system were twice as much as it is now, yet everything stayed the same size, your weight on Earth would

quadruple

Roll a bowling ball off the edge of a table. As it falls, its horizontal component of velocity

remains constant

The center of mass of a human body is located at a point

that changes as a person bends over

Neglecting air resistance, which will roll from rest to the bottom of an incline first, an empty jar, or the same jar filled with peanut butter?

the filled jar

A hunter on level ground fires a bullet at an angle of 2 degrees below the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first?

the fired one

A carnival has a Ferris wheel 1, where the seats are located halfway between the center and outside rim. A second Ferris wheel has seats that are on the outside rim. Both rotate at the same RPM. Compared to the first one, your angular speed while riding on the second Ferris wheel would be

the same, and your tangential speed is more

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

the target would be safer than the shooter

The speeds of the planets about the sun depend on

their distances from the sun

The tapered shape of the parts of the wheels that ride on railroad tracks allows opposite wheels to

travel at different linear speeds for the same rotational speed & in effect, vary their diameters

A 1000-kg car and a 2000-kg car are lifted the same distance. Raising the more massive car requires

twice as much work

One end of a long, uniform log is raised to shoulder level. Another identical log is raised at its center to the same level. Raising the second log requires about

twice as much work

If you find that twice as much work is needed to perform a task but it takes twice as much time, the amount of power required is

unchanged