Potential and Kinetic Energy of a Pendulum

Try this

Using the Accelerometer tool, fix the smartphone to the end of a simple pendulum made from a string attached to a point. Before releasing the pendulum from a given height (measured from the bottom of the pendulum swing), determine the potential energy using the mass of the smartphone and a ruler. Release the smartphone. Using data from the acceleration when at the lowest point, determine the tangential velocity at the lowest point (and hence, the kinetic energy).

Challenge yourself

• How did the starting potential energy at the top of the swing compare to the kinetic energy at the bottom of the swing?
• How would this relationship differ if potential energy had been measured from the ground, and not from the bottom of the pendulum swing? Why?
• Draw energy pie charts for systems in which potential energy is measured from both frames of reference.