: Energy causes things to happen. During the day, the sun gives off light and heat energy. As a car drives by you, it converts chemical energy, stored in the gasoline molecules, into mechanical energy. Our bodies convert the chemical energy in food into the kinetic energy to play or study.
Energy can be divided into two main types:
Potential Energy – energy that is stored (energy of position or height).
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If you stretch a rubber band, you will give it potential energy. As the rubber band is released, potential energy is changed to motion
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The chemical energy in a can of gasoline, the energy in a rubber ball before it is dropped, and the energy in water behind a dam are all examples of potential energy.
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-Gravitational potential energy is the energy stored in an object as the result of its height. The higher the object is, the greater its potential energy.
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There is a relationship between the mass(weight) of an object and its gravitational potential energy. The more massive (greater weight) an object is, the greater its potential energy.
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The formula for measuring the GPE of an object is weight (newtons) x height (meters)
Kinetic Energy – energy that is moving, (energy of motion).
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A rubber band flying through the air has kinetic energy, a bouncing ball has kinetic energy, and you have kinetic energy as you are walking to class.
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Kinetic energy is related to both mass and speed. The greater the mass or speed of an object, the greater the kinetic energy.
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Kinetic energy is the energy released by an object as it is doing work
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Different forms of kinetic energy can be changed into other forms.
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Kinetic energy, as well as other forms of energy, can be transferred from one object to another.
When energy is transferred or changes form, the total amount of energy stays the same. Energy cannot be created or destroyed, it just becomes changed in form.
Potential energy is converted into kinetic energy .
For example –
It does not take much effort to lift a ball off the ground. However, work is being done to the ball as it is being lifted, giving it energy. When the ball is dropped, the ball begins to move. The potential energy is converted into kinetic energy. The greater the original potential energy stored in an object, the greater the kinetic energy of motion produced.
You can increase the gravitational potential energy by increasing the height or weight of the object.
Energy is conserved . When you drop a ball, the potential energy is changed into kinetic energy. When the ball bounces to a lower and lower height, the energy is transferred. As the falling ball rubs against the air, some of the kinetic energy is changed into heat. Some energy changes into sound when the ball hits the floor. Because some energy becomes unusable when it changes from one form to another, the ball will never have enough energy to bounce back up to its starting height. In any conversion of energy, some of the energy becomes unavailable for future use. This fact of nature is called the Law of Conservation of
Energy.

To observe the relationship between potential and kinetic energy.
To calculate the Gravitational Potential Energy of golf balls dropped from different heights.
Be very careful with the balls. Do not throw them. DROP the balls as instructed in the procedure.
Golf ball
Meter stick
Masking tape
Spring Scale
Calculator
Pencil
1. Tape the meter stick vertically at the edge of the table, so that it is supported in place.
2. Hold the ball at the 50 cm mark and drop it.
3.Observe carefully as the ball bounces and record the height of the bounce (how high it came up again) in centimeters in the data table below.
4. Repeat steps 1-3 for a total of 5 trials (at the same drop height) Calculate the average bounce height of
Trials 1-5.
5. Hold the ball at the 75 centimeter mark and repeat step 3 & 4.
6. Hold the ball at the 100 cm mark and repeat steps 3 & 4.
Bounce
Height
Trial 1 Starting
Height
50 cm
(.5 meters)
Bounce
Height
Trial 2
Bounce
Height
Trial 3
Bounce
Height
Trial 4
Bounce
Height
Trial 5
Bounce
Height
Average
Bounce
Height
(convert to meters)
75 cm
(.75 meters)
100 cm
(1 meter)
GPE Calculations: Show all work
Procedure:
1.Tape a loop to the golf ball.
2. Hang the ball on the hook of the spring scale. Read the weight of the ball in Newtons (metric weight units) and record: ________
3. Use the formula:
GPE (joules) = Weight (newtons) x Height (meters) to determine the Gravitational Potential Energy
GPE(j) At 0.5 m : GPE(j) @ bounce height:
GPE(j) At 0.75 m: GPE(j) @ bounce height:
GPE(j) At 1.0 M: GPE(j) @ bounce height

:
Make a bar graph to compare the average bounce height (y axis) at different starting heights (x axis).
Remember to title the graph and label variable and units on each axis of your graph.
(use your results, background information and textbook pages 140-143)
1. Using the graphed data above and the background information, state the cause and effect relationship between the potential energy and the kinetic energy of the dropped ball.
2. When did the ball have the most potential energy in this investigation? Explain your answer.
3. How were you able to increase the amount of gravitational potential energy the ball had?
4. Explain another way you could increase the amount of gravitational potential energy in an object.
5. How is the potential energy in the ball changed to kinetic energy in this investigation?
6. How is kinetic energy in the ball changed back to potential energy in this investigation?
7. Not all of the ball’s potential energy was converted into kinetic energy. Where did this energy go?
8. A basketball player throws a ball into the air and catches it before it hits the ground.
Draw ( to the right)and label where the ball has the most potential energy and the most kinetic energy as it is thrown up and falls back down.