ELASTIC POTENTIAL ENERGY

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`Part 1: Launchers `
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`CONCEPTS: Elastic potential energy, kinetic energy `
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`BACKGROUND: The potential energy of a stretched rubber band turns into `
`kinetic energy of a projectile when a sling shot is released.  `
`The KE of the launched object can be measured from the effect on a box that catches it `
`and pushed across a smooth surface  (see other KE activities). `
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`EQUIPMENT NEEDED: A board approx. 1" x 6" x 2 ft (make your own design), `
`rubber bands, plastic sheeting, strong tape, eg. duct tape, nails, s`
`mall balls of various mass: tennis, handball, golf ball, baseball etc., weights of any kind `
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`ACTIVITY: Construct a rubber band powered ball launcher.  `
`The cradle for the launched balls can be made by applying duct tape to some plastic sheet `
`and cutting out an oval shape as indicated.  Punch holes in the ends with a paper punch `
`to attach the rubber bands. `
`Measure the elastic potential energy the rubber band launcher has by holding it vertically `
`and stretching the rubber band by resting a weight on it.  `
`Mark the end of stretch for one weight and then another for twice as much weight `
`(this will be the point for twice as much elastic potential energy).   `
`Cut up a cardboard box to act as a catcher for the launched balls.  `
`Experiment with the design of your catcher until you get one that contains the ball with a `
`minimum of bouncing around.   `
`The distance that the box is pushed by the ball is a measure of the ball's kinetic energy.  `
`Examine the effects of different balls and different lengths of rubber band stretch, etc. `
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`CONNECTIONS: Bows and arrows, sling shots, etc.`
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Part 2: Rubber band racers

CONCEPTS: Elastic potential energy, kinetic energy, force, friction

EQUIPMENT NEEDED: thread spools and other spools of any type

(eg. from wire, etc., or, cans with lids, rubber bands, sticks, washers)

ACTIVITY: Have students construct and race these wind up toys:

Many variations on this design are possible. Urge student to experiment with different designs.

Larger racers can be made from cans with replaceable lids (eg. coffee cans instead of spools.

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`Part 3: Toys that work with elastic PE `
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` CONCEPTS: elastic potential energy, measurement, kinetic energy `
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`BACKGROUND: Many common toys store elastic potential energy in springs, rubber bands `
`or compressed air. `
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`EQUIPMENT NEEDED: Toys such as: dart guns, helicopter guns, water rockets, squirt guns, `
`especially the kind you can pump up. `
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`ACTIVITY: Study how the toys work.  Collect and analyze data on how many pumps, `
`wind-ups or whatever, lead to how much of a result.`