ELASTIC POTENTIAL ENERGY

 
Part 1: Launchers 
 
CONCEPTS: Elastic potential energy, kinetic energy 
 
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). 
 
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 
 
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. 
 
CONNECTIONS: Bows and arrows, sling shots, etc.
 

 

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:
http://webpages.marshall.edu/~bady/RICK/elastic2.GIF

 

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.

 
Part 3: Toys that work with elastic PE 
 
 CONCEPTS: elastic potential energy, measurement, kinetic energy 
 
BACKGROUND: Many common toys store elastic potential energy in springs, rubber bands 
or compressed air. 
 
EQUIPMENT NEEDED: Toys such as: dart guns, helicopter guns, water rockets, squirt guns, 
especially the kind you can pump up. 
 
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.