Calculating the potential energy (PE) of a falling object is a fairly simple process involving only a few numbers and a bit of arithmetic. To figure out the change in potential energy, you do the calculation twice: once for the starting position, once for the final position, then you subtract the second energy result from the first.
TL;DR (Too Long; Didn't Read)
Change in potential energy (PE) is PE(change) = PE(initial) - PE(final)
Measure Initial Values
Measure the initial height and mass of the object. Record your values.
Calculate Initial PE
Calculate your object's initial potential energy using the following equation: potential energy (PE) = mass * gravity * height. Use the height and mass you measured along with 9.8 m/s2 as the constant for gravity. The result will be your initial potential energy.
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Measure Final Values
Determine the object's final height and mass. Record your values.
Calculate Final PE
Compute the object's final potential energy. Use the same equation as before while still using 9.8m/s2 as the constant for gravity. But, this time use your object's final height and mass. This number will be your final potential energy.
Calculate the Difference
Use the following equation to determine change in potential energy: Change in PE = Final PE – Initial PE. The final number is your change in potential energy.