Motion, Forces and Energy

Energy transformations found in everyday life will be emphasized. Students should know that an object at rest has potential energy and an object in motion has kinetic energy. Students should also understand that energy transformations occur in energy production, as in the conversion of wind energy to electrical energy.

KEY TERMS

• An energy transformation occurs when energy changes from one form to another.

• Energy transformations occur in energy production (as in conversions of energy for use in everyday life).

• Potential Energy is the energy that is stored because of an object’s position.

• The energy of an object due to its motion is called Kinetic Energy.

POSITION 1

POSITION 2

POSITION 3

Potential Energy

Kinetic Energy

Potential Energy

The boulder is in aresting position with low potential energy and no kinetic energy.

EXAMPLE 1

The boulder at the top of the hill has potential energy and no kinetic energy.

As the boulder rolls down the hill, the potential energy transforms into kinetic energy and kinetic energy becomes greater until

When a student rides a bike down a hill, potential energy is transferred into kinetic energy.

Potential Energy

Kinetic Energy

EXAMPLE 2

The amount of kinetic energy also depends on the mass and the speed of an object. Kinetic energy increases as speed increases. The faster an object moves, the more kinetic energy it has.

EXAMPLE 3:

The faster a bowling ball moves, the harder it will strike the pins, the more pins it can knock down.

As the ball leaves the ground, it is moving the fastest and has the maximum kinetic energy. As the ball moves upward, it slows down as it’s kinetic energy is transformed into potential energy. As the ball moves downward, it speeds up as its potential

energy is transformed into kinetic energy.

1

2

3

EXAMPLE 4

Explain how energy is transformed as the ball rises and falls.

The boulder would have the greatest kinetic energy at which of the positions on the waterfall?

A

B

A position 1

B position 2

C position 3

D position 4

1

2

3

4

B position 2

QUESTION

A yo-yo can demonstrate both Potential and Kinetic energy. When does a yo-yo have it greatest potential energy?

A In the hand before the yo-yo is releasedB At the bottom of the stringC When the yo-yo is fallingD When the yo-yo is climbing the stringA In the hand before the yo-yo is released.

Which will have the most kinetic energy rolling down the hill?

A TruckB BallC RunnerD All of the are examples of Potential energy.

Answer: A

Examples of Energy Transformations

Your body converts chemical energy in food into energy ….

it needs to move,think,grow and heat the body.

Examples of Energy Transformations

An electric current that flows in a wire carries electrical energy that can be

used in

many ways. A stove transforms electrical energy to heat energy that boils the water and cooks food.

A lightbulb converts electrical energy into light energy when you flip a switch.

Examples of Energy Transformations

The most common windmills convert the kinetic energy of the wind into rotary motion of the generator. The rotating generator, typically a direct-drive permanent magnet alternator, produces electricity.

The chemical fuel is transformed into thermal and mechanical energy needed to run the car.

Which of the following can be used to transform chemical energy into heat energy?

A. melting a candle

B. lighting a match

C. solar panels

D. a light bulb

Answer: B

Answer: D

Which of these types of energy conversions

occurs in a battery-powered flashlight?

A. A. Thermal to mechanical

B. Light to electrical

C. Thermal to chemical

D. Chemical to electrical