Physlet Illustration: Work Done by a Spring

 

 
A block of mass 20 kg is attached to a wall by a horizontal spring of force constant k = 10 N/m. The block rests on a frictionless floor. Pull or push the block away from its equilibrium location, and then push "Play" to watch it move back and forth. Study the graph of both the work done on the spring and the block's kinetic energy as functions of time. How do they compare? Why?

Hints

  1. When you first displace the block, work is done on the spring.
  2. After you let go, the block returns to its equilibrium position.
  3. How much (net) work has been done on the spring by this time?
  4. What is the block's speed at this time?
  5. What about its kinetic energy?
  6. What can you conclude about the relationship between work done on the spring and the block's kinetic  energy?

Reference

See Walker, Section 7-3

Illustration written by Steve Mellema