Physics exam 1

A ball is thrown upwards and returns to the same position. Compared with its original speed after release, its speed when it returns is about ____.

the same

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 mass at the earth's surface weighs about _____.

10 N

If more horizontal force is applied to a sliding object than is needed to maintain a constant velocity.

the object accelerates in the direction of the applied force

When a falling object has reached its terminal velocity, its acceleration is ______.

zero

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

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

If experimental results are not reproducible then ____.

The results are not considered valid

The synthesis of a large collection of information that contains well-tested and verified hypotheses about certain aspects of the world is known as a scientific

Theory

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

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

add up to equal your weight

What causes a change in acceleration?

air resistance, applied force, and its mass

A 10-N falling object encounters 4 N of air resistance. The net force on the object is _____.

6 N.

The vertical height attained by a basketball player who achieves a hang time of a full 1 s is ____.

1.25

A man leans over the edge of a cliff and throws a rock upward at 5 m/s. How far below the level from which it was thrown is the rock 2 seconds later?

10 m

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.

If a projectile is fired straight up at a speed of 10 m/s, the total time to return to its starting position is about _____.

2 sec

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

2400 N

A girl pulls on a 10-kg wagon with a constant horizontal force of 30 N. If there are no other horizontal forces, what is the wagon's acceleration in meters per second per second?

3.0 m/s/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

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 10-kilogram block with an initial velocity of 10 m/s slides 10 meters across a horizontal surface and comes to rest. It takes the block 2 seconds to stop. The stopping force acting on the block is about _____.

50 N

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?

50 m/s

When a woman stands at rest with both feet on a scale, it reads 500 N. When she gently lifts one foot, the scale reads _____.

500 N

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

If a car increases its velocity from zero to 60 km/h in 10 seconds, its acceleration is ____.

6km/h/s

In science an educated guess is called

A hypothesis

A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is ____.

Zero

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

about 0.5 g ( 0.5 * 10 m/s/s )

A 1-kg rock that weighs 10 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 ______.

about 10 N

If you drop an object, it will accelerate downward at a rate of about 10 meters per second per second. If you instead throw it downwards, its acceleration (in the absence of air resistance) will be _____.

about 10 m/s

What are two vector quantities?

acceleration and velocity

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

A large and a small person wish to parachute at equal terminal velocities. The larger person will have to ____.

get a larger parachute.

A 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 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 how much acceleration

has 0 acceleration

A skydiver steps from a helicopter and falls for a few seconds until he reaches his terminal velocity. Thereafter, until he opens his parachute, his acceleration

is zero

A pair of tennis balls fall through the air from a tall building. One of them is filled with lead pellets. The ball to reach the ground first is the _____.

lead-filled ball

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

During the time of the year when the Earth starts moving closer to the sun, the sun

moves toward the Earth, but a smaller distance

A horse exerts 500 N of force on a heavy wagon. The wagon pulls back on the horse with an equal force. The wagon still accelerates because ___.

nevertheless there is still an unbalanced force on the wagon

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

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.

The attraction of a person's body toward the Earth is called weight. The reaction to this force is

the person's body pulling on the Earth

A feather and a coin will have equal accelerations when falling in a vacuum because

the ratio of each object's weight to its mass is the same

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

velocity is 0 and its acceleration is 10m/s/s