In the first of this series of labs exploring the role of energy in change, you found that the energy stored in an elastic system was proportional to the square of the change in the length of the spring or rubber band deformed by the applied force. We called the energy stored in this way elastic energy.

This energy can be transferred to another object to produce a change–for example, when the spring is released, it can launch a toy dart. It seems reasonable that the more the spring is compressed, the greater the change in speed it can impart to the object. As the spring or band returns to its original shape, it transfers energy to the moving object. We say that the moving object stores energy in an account called kinetic energy. It seems reasonable that an object’s kinetic energy is a function of its mass and velocity. It would be useful to determine a quantitative relationship between the kinetic energy and its velocity for a given mass.


In this experiment, you will

  • Recognize that the energy stored in an elastic system (spring, rubber band) can be transferred to another object, resulting in a change in the state of that object.
  • Determine an expression for the kinetic energy stored in a moving body.