Swinging Pendulum Engineering Lab

Background Info This activity shows the engineering importance of understanding the laws of mechanical energy. More specifically, it demonstrates how potential energy can be converted to kinetic energy and back again. Given a pendulum height, you will calculate and predict how fast the pendulum will swing by using the equations for potential and kinetic energy as you experimentally measure the speed of the pendulum and compare theory with reality.

PE-KE Remember that an object's potential energy (PE) is due to its position (height), and an object's kinetic energy (KE) is due to its motion (velocity). Potential energy can be converted to kinetic energy by allowing the object to fall (for example, a roller coaster going down a hill or a book falling off a table). This energy transformation also holds true for a pendulum, as illustrated in the diagram. (next slide)

Energy Conversion As a pendulum swings, its potential energy converts to kinetic and back to potential, as illustrated in Figure 1.

What we are doing In this activity, you will prove that the transformation of energy occurs by calculating the theoretical value of velocity at which a pendulum should swing and comparing it to a measured value. You will also compare the periods (the length of time it takes the pendulum to swing back and forth one time) of the pendulum by allowing it to swing from two different heights.

Equations Four equations will be used in this activity: PE = m∙g h KE = ½ m∙V 2 V m = distance ÷ time T = (2∙Π∙ ( l / g )½ T=2pi√l/g –l is the length of the pendulum (m) –Vt is the calculated velocity (m/s) –Vm is the measured velocity (also m/s), –T is the period of the pendulum(s). To make the calculations simpler, use the metric system for measurements and calculations