Science exam

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

A machine puts out 100 Watts of power for every 1000 Watts put into it. The efficiency of the machine is

10%

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

10N

The force of friction on a sliding object is 10 newtons. The applied force needed to maintain a 31) constant velocity is

10N

If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by about

10m/s

A tow truck exerts a force of 3000 N on a car, accelerating it at 2 meters per second per second. 34) What is the mass of the car?

1500kg

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

16 times the KE

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 seconds

A car has a mass of 1000 kg and accelerates at 2 meters per second per second. What is the 33) magnitude of the net force exerted on the car?

2000N

Two projectiles are fired from ground level at equal speeds but different angles. One is fired at an angle of 30 degrees and the other at 60 degrees. The projectile to hit the ground first will be the one fired at (neglect air resistance)

30 degrees

If a rocket initially at rest accelerates at a rate of 50 m/s2 for one minute, its speed will be

3000m/s

A TV set is pushed a distance of 2 m with a force of 20 N. How much work is done on the set?

40 J

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?

400N

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

40m/s

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

500

Using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed to do this job was

50W

An object is pulled northward by a force of 10 N and at the same time another force of 15 N pulls it 30) southward. The magnitude of the resultant force on the object is

5N

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

6km/h/s.

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

6n

A projectile is launched at ground level an angle of 15 degrees above the horizontal and lands down range. What other projection angle for the same speed would produce the same down-range distance?

75 degrees

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

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

About 180m

Disregarding air resistance, objects fall with constant

Acceleration

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

Acceleration

Without air resistance, a projectile fired horizontally at 8 km/s from atop a mountain would

All of the

Which has zero acceleration? An object

All of these

According to Newton's law of inertia, a railroad train in motion should continue going forever even if its engine is turned off. We never observe this because railroad trains

Always have forces that oppose their motion

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 two measurements necessary for calculating average speed are

Distance and time

The newton is a unit of

Force

If an object falling freely were somehow equipped with an odometer to measure the distance it travels, then the amount of distance it travels each succeeding second would be

Greater than the second before

An object following a straight-line path at constant speed

Has zero acceleration

When an automobile is braked to a stop, its kinetic energy is transformed to

Heat

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

Increases

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

Inertia

An object may have potential energy because of its

Location

Compared to the period of satellites in orbit close to the Earth, the period of satellites in orbit far 99) from the Earth is

Longer

A kilogram is a measure of an object's

Mass

A large metal ball is shot from a cannon with a short barrel. If the same ball were to be shot from cannon with a longer barrel, its muzzle velocity would be

More

An object that has kinetic energy must be

Moving

While a car travels around a circular track at a constant speed, its

None of the above

Acceleration is greater for a satellite when it is at the

Perigee

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

Compared to the mass of a certain object on Earth, the mass of the same object on the moon is

The same

The ball rolling down an incline has its maximum potential energy at

The top

An object is propelled along a straight-line path by a force. If the net force were doubled, the 29) object's acceleration would be

Twice as much

If an object is raised twice as high, its potential energy will be

Twice as much

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

Twice as much work

While an object near the Earth's surface is in free fall, its

Velocity Increases

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

Passengers in a high-flying jumbo jet feel their normal weight in flight, while passengers in the orbiting space shuttle do not. This is because passengers in the space shuttle are

Without support forces

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

Zero

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

Zero

Which of the following has the largest momentum relative to the Earth's surface?

a pickup truck speeding along a highway

When you jump from an elevated position you usually bend your knees upon reaching the ground. By doing this, you make the time of the impact about 10 times as great as for a stiff-legged landing. In this way the average force your body experiences is

about 1/10 as great

Which of the following is not a compound?

air

The circular path of a satellite orbiting the Earth is characterized by a constant

all of these

The amount of gravitational force that acts on the space shuttle while in orbit is

almost as much as the shuttle's weight on the Earth's surface

Inside a freely falling elevator, there would be no

apparent weight for you

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

arrow's push against the bowstring

A bullet fired horizontally from a rifle begins to fall

as soon as it leaves the barrel

Neglecting friction, a large block of ice and a small block of ice start sliding down an incline 37) together. The heavier block will get to the bottom

at the same time as the light block.

Earth satellites are typically more than 100 km high so as to be above the Earth's

atmosphere

A very massive object A and a less massive object B move toward each other under the influence of gravitation. Which force, if either, is greater?

both forces are the same

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

If no external forces are acting on a moving object, it will

continue moving at the same velocity

Suppose a particle is being accelerated through space by a 10-N force. Suddenly the particle encounters a second force of 10 N in the opposite direction from the first force. The particle with both forces acting on it

continues at the speed it had when it encountered the second force

A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its vertical component of velocity

decreases

According to Newton, doubling the distance between two interacting objects

divides by 4 the gravitational force between them

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

earth

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

ellipses

A vertically oriented rocket that is somehow able to maintain a continuous upward velocity of 8 km/s will

escape from the Earth.

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

exhaust gases

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

An Earth satellite is simply a projectile

freely falling around the earth

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

greater

According to Newton, the greater the masses of interacting objects, the

greater the gravitational force between them

A skydiver's terminal velocity will be greatest if she falls

head first

If your automobile runs out of fuel while you are driving, the engine stops but you do not come to an abrupt stop. The concept that most explains why is

inertia

For an action force, there must be a reaction force that

is exactly equal in magnitude

The main reason ocean tides exist is that the pull of the moon

is greater on oceans closer to the moon and less on oceans farther from the moon

A ball is thrown upwards and caught when it comes back down. In the presence of air resistance, 20) the speed with which it is caught is always

less than the speed it had when thrown upwards.

A force is a vector quantity because it has both

magnitude and direction.

An astronaut , floating alone in outer space, throws a baseball. If the ball floats away at a speed of 20 meters per second, the astronaut will

move in the opposite direction, but at a lower speed.

An Earth satellite is in an elliptical orbit. The satellite travels fastest when it is

nearest the Earth

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

no work on the wall is done in either case

A satellite in an elliptical orbit travels at constant

none of these

The period of a satellite, the time it takes for a complete revolution, depends on the satellite's

radial distance

A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its horizontal component of velocity

remains unchanged

A rifle recoils while firing a bullet. The speed of the rifle's recoil is small because the

rifle has much more mass than the bullet

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

size and speed of the object

If we doubled the magnifying power of the most powerful optical microscope in the world, we would

still not be able to see or photograph an atom

Your weight is

the gravitational attraction force between you and the Earth.

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.

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

the object eventually slides to a stop

The speeds of the planets about the sun depend on

their distances from the sun

Planets would crash into the sun if it weren't for

their tangential velocities

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

three times the usual power output.

To catch a ball, a baseball player extends the hand forward before impact with the ball and then lets 51) it ride backward in the direction of the ball's motion. Doing this reduces the force of impact on the player's hand principally because the

time of impact is increased

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.