### Two factors that greatly affect air resistance on falling objects are the

size and speed of the object

### No work is done by gravity on a bowling ball that rolls along a bowling alley because

the force on the ball is at right angles to the ball's motion.

### If the mass of an object does not change, a constant net force on the object produces constant

acceleration.

### A truck is moving at constant velocity. Inside the storage compartment, a rock is dropped from the midpoint of the ceiling and strikes the floor below. The rock hits the floor

exactly below the midpoint of the ceiling.

### A skydiver jumps from a high-flying plane. As her velocity of fall increases, her acceleration

decreases.

### A block is dragged without acceleration in a straight-line path across a level surface by a force of 6 N. What is the force of friction between the block and the surface?

6 N

### A heavy object and a light object are dropped at the same time from rest in a vacuum. The heavier object reaches the ground

at the same time as the lighter object.

### 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.

### A bird sitting on the limb of a tree is moving about 30 km/s with respect to the sun. If the bird takes 1 second to drop down to a worm below, the worm would be 30 km downrange from the bird when it reached the ground. This faulty reasoning is best countered with Newton's

first law.

### A 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with respect to the ground?

80 J

### A light woman and a heavy man jump from an airplane at the same time and open their same-size parachutes at the same time. Which person will get to a state of zero acceleration first

the light woman

### The last instant just before an airplane crashes a passenger jumps out the door and falls only two feet to the ground. The passenger is

probably hurt or killed

### An object falls freely from rest on a planet where the acceleration due to gravity is 20 meters per second squared. After 5 seconds, the object will have a speed of

100 m/s

### A car accelerates at 2 meters per second per second. Assuming the car starts from rest, how much time does it need to accelerate to a speed of 30 m/s?

15 seconds

### When a rock thrown straight upwards gets to the exact top of its path, its

velocity is zero and its acceleration is about 10 meters per second per second.

### If you drop an object, it will accelerate downward at a rate of 9.8 meters per second per second. If you instead throw it downwards its acceleration( in the absence of air- resistance) will be

9.8 meters per second per second

### A car traveling at 22 m/s comes to an abrupt halt in 0.1 second when it hits a tree. What is the deceleration in meters per second per second of the car?

220

### A baseball player bats a ball with a force of 1000 N. The reaction force that the ball exerts against the bat is

1000 N

### Hang from a pair of gym rings and the upward support forces of the rings will always

add up to equal your weight

### An object lifted 10 meters gains 200 J of potential energy. If the same object is lifted 20 meters, its potential energy gain is

twice as much

### Disregarding air drag, how fast must you toss a ball straight up in order for it to take 2 seconds to return to the level from which you tossed it?

10 m/s

### A 1000-kg automobile enters a freeway on-ramp at 20 m/s and accelerates uniformly up to 40 m/s in a time of 10 seconds. How far does the automobile travel during that time?

300 m

### An object, at rest near the surface of a distant planet, starts to fall freely . If the acceleration there is twice that of the earth, its speed one second later would be

20 m/s

### It takes 40 J to push a large box 4 m across a floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box?

10 N

### A person is attracted toward the center of the Earth by a 500-N gravitational force. The Earth is attracted toward the person with a force of

500 N.

### A 500-N parachutist opens his chute and experiences an air resistance force of 800 N. The net force on the parachutist is

300 N upward.

### If an object moves with constant acceleration, its velocity must

change by the same amount each second.

### A 10-kg brick and a 1-kg book are dropped in a vacuum. The force of gravity on the 10-kg brick is

10 times as much

### A Mack truck and a Volkswagen traveling at the same speed have a head-on collision. The vehicle that undergoes the greatest change in velocity will be the

Volkswagen.

### If you push for a half hour or a whole hour against a stationary wall

no work is done in either case.

### A sheet of paper can be withdrawn from under a container of milk without toppling it if the paper is jerked quickly. This best demonstrates that

the milk carton has inertia.

### A rock weighs 30 N on Earth. A second rock weighs 30 N on the moon. Which of the two rocks has the greater mass?

the one on the moon

### A jumbo jet has a mass of 100,000 kg. The thrust for each of its four engines is 50,000 N. What is the jet's acceleration in meters per second per second when taking off?

2

### A car maintains a constant velocity of 100 km/hr for 10 seconds. During this interval its acceleration is

zero

### A bullet is dropped into a river from a very high bridge. At the same time, another bullet is fired from a gun, straight down towards the water. Neglecting air resistance, the acceleration just before striking the water

is the same for each bullet.

### A 1-kg rock that weighs 9.8 N is thrown straight upward at 20 m/s. Neglecting air resistance, the net force that acts on it when it is half way to the top of its path is

9.8 N.

### An object is propelled along a straight-line path by a force. If the net force were doubled, the object's acceleration would be

twice as much.

### If a rocket initially at rest accelerates at a rate of 50 m/ for one minute, its speed will be

3000 m/s.

### An coconut and a feather fall from a tree through the air to the ground below. The amount of air-resistance force is

greater on the coconut.

### An object is pulled northward by a force of 10 N and at the same time another force of 15N pulls it southward. The magnitude of the resultant force on the object is

5 N.

### The force of friction on a sliding object is 10 newtons. The applied force needed to maintain a constant velocity is

10 N.

### A skydiver, who weighs 500 N, reaches terminal velocity of 90 km/h. The air resistance on the diver is then

500 N.

### A sack of potatoes weighing 200 N falls from an airplane. As the velocity of fall increases, air resistance also increases. When air resistance equals 200 N, the sack's acceleration in meters per second per second is

0.

### An object covers a distance of 8 meters in the first second of travel, another 8 meters during the next second , and 8 meters again during the third second. Its acceleration in meters per second per second is approximately

0

### Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the tendency of the rock is to

follow a straight-line path.

### A ball is thrown upwards. Neglecting air resistance, what initial upward speed does the ball need to remain in the air for a total time of 10 seconds?

about 50 m/s

### 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 has a mass of 1000 kg and accelerates at 2 meters per second per second. What is the magnitude of the net force exerted on the car?

2000 N

### What task requires the most work; lifting a 50-kg sack 2 meters or lifting a 25-kg sack 4 meters?

Both require the same amount of work.

### A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always

opposite its velocity

### An object falls freely from rest on a planet where the acceleration due to gravity is twice as much as it is on Earth. In the first 5 seconds it falls a distance of

250 m.

### It takes 6 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft?

about 180 m

### If you do work on an object in one-third the usual time, your power output is

three times the usual power output.

### If a non-rotating object has no acceleration, then we can say for certain that it is

in mechanical equilibrium.

### An archer shoots an arrow. Consider the action force to be exerted by the bowstring against the arrow. The reaction to this force is the

arrow's push against the bowstring.