Physics Unit II

The muzzle velocity of a bullet fired from a new rifle is 100 m/s. Neglecting air resistance, at the end of one second a bullet fired straight up into the air will have traveled a distance of

(100 - 4.9) m

An apple at rest weighs 1 N. The net force on the apple when it is in free fall is

1 N

A 1-kg ball is thrown at 10 m/s straight upward. Neglecting air resistance, the net force that acts on the stone when it is halfway to the top of its path is about

10 N

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 horse gallops a distance of 10 kilometers in a time of 30 minutes. It's average speed is

20 km/h

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

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

If an object's mass is decreasing while a constant force is applied to the object, the acceleration

Increases

A skydiver of mass 100 kg experiences air resistance of 500 N, and an acceleration of

about 0.5 g

A ball is thrown 125 meters upward and then falls the same distance back to Earth. Neglecting air resistance, its total time in the air is

about 10 seconds

Disregarding air resistance, objects fall with constant

acceleration

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

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

directed downward

The newton is a unit of

force

Consider drops of water that leak at a steady rate from a dripping faucet. As the drops fall they

get farther apart

An object is propelled along a straight-line path in space by a force. If the mass of the object somehow becomes twice as much, its acceleration

halves

An object following a straight-line path at constant speed

has zero acceleration

Two objects of the same size, but unequal weights are dropped from a tall tower. Taking air resistance into consideration, the object to hit the ground first will be the

heavier object

Wherever the is an action force, there must be a reaction force which

is exactly equal in magnitude

A ball is thrown vertically into the air. Because of air resistance, its speed when it returns to its starting level compared with its initial speed is

less

A ball thrown straight upward takes 10 seconds to go up and return to the ground. Because of air resistance, the time taken for the ball just to go up is

less than 5 s

A kilogram is a measure of an object's

mass

The maximum acceleration of a car while towing a second car twice its mass, compared to its acceleration with no car in tow, is

one third

As a ball falls, the action force is the pull of the Earth's mass on the ball. The reaction force is the

pull of the ball's mass on the Earth

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

size and speed of the object

Galileo's use of inclined planes allowed him to effectively

slow down the acceleration of free fall

A rocket becomes progressively easier to accelerate as it travels upward from the ground mainly because

the mass of the rocket decreases as fuel is burned

Drop a rock from a 5-m height and it accelerates at 10 m/s 2 and strikes the ground 1 s later. Drop the same rock from a height of 2.5 m and its acceleration of fall is about

the same amount

A car traveling at 100 km/hr strikes an unfortunate bug and splatters it. The force of impact is

the same for both

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

Joe pushes Bill, who is asleep. Bill

pushes Joe equally hard even without waking up

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

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

What horizontally-applied force will accelerate a 400-kg crate at 1 m/s 2 across a factory floor against a friction force half its weight?

2400 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

A karate chop delivers a blow of 3000 N to a board that breaks. The force that acts on the hand during this event is

3000 N

Two people, one twice as massive as the other, attempt a tug-of- war with 12 meters of massless rope on frictionless ice. After a brief time, they meet. The heavier person slides a distance of

4 m

At one instant a heavy object in air is moving upward at 50 meters per second. One second later its speed in meters per second is approximately

40 m/s

A man weighing 800 N stands at rest on two bathroom scales so that his weight is distributed evenly over both scales. The reading on each scale is

400 N

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

One half second after starting from rest, a freely-falling object will have a speed of about

5 m/s

A rock is thrown vertically into the air. At the top of its path, its acceleration in meters per second per second is

9.8

A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. How far below the level from which it was thrown is the rock 2 seconds later?

9.8 m

When you relax at rest with your left foot one bathroom and your right foot on a similar scale, each of the scales will

Any of the above may be correct

If one object has twice as much mass as another object, it also has twice as much

inertia

In which case would you have the largest mass of gold? If your chunk of gold weighed 1 N on the

moon

A ball is thrown vertically into the air. Because of air resistance, its time coming down compared to its time going up is

more

Twelve seconds after starting from rest, an object falling freely will have a speed of

more than 100 m/s

At one instant an object in free fall is moving downward at 50 meters per second. One second later its speed should be about

60 m/s

A bullet is dropped from the top of the Empire State Building while another bullet is fired downward from the same location. Neglecting air resistance, the acceleration of

each bullet is 9.8 meters per second per second