Energy

When you do 100 J of work on a sled that slides without friction, its KE increases by

100 J

When you do 1000 J of work on a car jack and the gravitational potential energy of the car is increased by 300 J, the efficiency of the jack is

30%

A shiny sports car at the top of a vertical cliff has a potential energy of 100 MJ relative to the ground below. Unfortunately, a mishap occurs and it falls over the edge. When it is halfway to the ground, its kinetic energy is

50 MJ

When 100 J are put into a device that puts out 60 J, the efficiency of the device is

60%

Is the following statement True or False? A ball thrown straight up in the air has its maximum kinetic energy half way to the top of its path.

False

Is the following statement True or False? A low-mass molecule and a high-mass molecule moving with the same kinetic energy have equal speeds.

False

Is the following statement True or False? The law of energy conservation does not apply to nuclear reactors

False

Is the following statement True or False? When the speed of an object is doubled, its change in kinetic energy also doubles.

False

Is the following statement True or False? A ball tossed straight up in the air has it's maximum potential energy at the top of its path.

True

Is the following statement True or False? A dog and a mouse running with the same kinetic energy have unequal speeds.

True

Is the following statement True or False? If you do 100 J of work on a cart, it's energy will increase by 100 J.

True

Is the following statement True or False? The faster a machine can do a given amount of work, the more power it expends.

True

Is the following statement True or False? The kinetic energy of a roller coaster is greater at lower elevations than at higher elevations.

True

Is the following statement True or False? The potential energy of a roller coaster is greater at higher elevations than at lower elevations.

True

Mechanical energy applies to

both potential and kinetic energy

You're coasting in a car going at 40 km/h on a level road and brake to 20 km/h. When you take your foot off the brake pedal, the car tends to

continue at 20 km/h

Whereas impulse involves force and time, work involves force and

distance

When a hybrid car brakes to a stop, much of its kinetic energy is transformed to

electric potential energy

A simple machine cannot multiply

energy

When a ball starting from rest rolls down an inclined plane, its potential energy relative to the bottom of the plane is

equal to it's kinetic energy when half way down

Which of these forms of energy is not renewable?

fossil fuel power

Raising an auto in a service station increases its gravitational potential energy. Raising it four times as high increases its potential energy by

four times

When two identical cars, one traveling twice as fast as the other, brake to a stop using old-fashioned brakes, the faster car will skid

four times as far

A model airplane moves twice as fast as another identical model airplane. Compared with the kinetic energy of the slower airplane, the kinetic energy of the faster airplane is

four times as much

An empty truck traveling at 10 km/h has kinetic energy. How much kinetic energy does it have when its speed is doubled?

four times the kinetic energy

After a car is raised in a service station, we say the car has increased

gravitational potential energy

The kinetic energy of a cannonball fired from a cannon is

greater than the kinetic energy of the recoiling cannon

A moving freight car slams into another identical freight car at rest. The two cars stick together and move along the track. The speed of the coupled cars compared with the initial speed of the first car is

half

When a car is braked to a stop, unless it is a hybrid, its kinetic energy is transformed to

heat

A circus performer diving off a tall pole has just as much kinetic energy as potential energy relative to the ground, when she

is half way to the bottom

If a charging elephant has kinetic energy, it must also have

momentum

When an increase in speed doubles the momentum of a moving body, its kinetic energy

more than doubles

An empty truck traveling at 10 km/h has kinetic energy. How much kinetic energy does it have when its speed and mass are doubled?

more than four times the KE

A dog and a mouse run down the road with the same KE. The faster moving one is the

mouse

Living cells...

need an energy source

Which of the following can multiply force?

seesaw, lever, system of pulleys

When work is done twice as quickly, then the power expended is

twice

Lifting a sack of potatoes and placing it on a shelf increases the potential energy of the sack. If you lift the sack and place it on a shelf twice as high in half as much time, the increase of potential energy of the sack is

twice as much

Raising a heavy load requires work. The power expended in raising it in half the time is

twice as much

A 1-kg ball has twice the speed as a 2-kg ball. Compared with the 1-kg ball, the 2-kg ball has

twice the kinetic energy

Raising an auto in a service station requires work. Raising it twice as high requires

twice the power

Raising a heavy load requires work. Raising it twice as high requires

twice the work

The most energy per unit mass can be extracted from

uranium