 # Categories of Energy

## Introduction:

Energy exists in many forms all around us. The development of our modern society has been accomplished because scientists and engineers have learned to capture some of that energy and transform it into ways to do useful work. For example, the conversion of energy from a chunk of coal into steam and then into mechanical engines that can do heavy work was important in the 19th century and the industrial revolution.

Engineers must know where to "find" energy resources and then how to convert them into forms that are more useful for all of the machines and gadgets we use in our daily lives.

Look around this room: What tools or devices are using energy? Lights are a good example. They convert electric energy into light energy.

The goal of today's lesson is to explore some critical terms that are needed for energy – forms of energy and states of energy.

## Potential vs. Kinetic Energy

Potential (stored energy)

PE=mass*gravity*height

PE=mgh

Kinetic (energy in motion)

KE=1/2*mass*velocity

KE=1/2mv

Questions based on Potential and Kinetic Energy:

1. If I drop a bowling ball and a golf ball from the same height, which has more potential energy? What about kinetic energy?
2. If I drop two golf balls from different heights, which has more PE?
3. If I drop one golf ball, and throw the other one down from the same height, which has more KE?

## The Cup Crusher!

• Place a paper cup on the floor and hold a small weight or baseball, 6 inches above the cup.
• Drop the ball and point out that the ball starts out with potential energy and converts to kinetic energy,
• Repeat for a height of 12 inches and 36 inches.
• Where is the energy coming from that is lifting the ball. Does it require more energy to lift the ball higher?
• Predict the behavior.
• Now use a bowling ball, or heavier weight.

## Exit Ticket

1. How did the ball dropping activity demonstrate a transfer of energy? Use the vocabulary: Height, Potential and Kinetic Energy in your answer.
2. If the mass of an object is 10 kg, and it is dropped from a height of 5 m, what is its potential energy?