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Potential Energy

An object has not only kinetic energy (the energy of motion), but also potential energy. Potential energy has nothing to do with motion. An object's potential energy is determined by its position relative to the ground. Potential energy is equal to the product of an object's weight (m x g) and its height:(h).

Problem:
A 50 kilogram object is located 5 meters above the ground level. Find its potential energy.

Solution:

Step 1:

In this problem we are given the following: m= 50 kg g = 9.8 m/s2 h = 5 m

Step 2:

Plug the data into the given formula:

Answer: The object's potential energy is 2450 J.

Problem:
A 12 kg cat who is resting on a tree has a potential energy of 50 J. Calculate its position (height) relative to the ground.

Solution:

Step 1:

In this problem we are given the following:

m =12 kg
g = 9.8 m/s
PE = 50 J

Step 2:

Plug the data into the formula and solve the problem:

In order to find h we must divide both sides of the equation by 117.6

Answer: The cat is located 0.43 m above the ground.

Problem:
A girl runs up a 5 meter high flight of stairs and she has 1000 J of potential energy at the top. Calculate her mass.

Solution:

Step 1:

In this problem we are given the following:

PE = 1000 J
g = 9.8 m/s
h = 5 m

Step 2:

Plug the data into the formula:

In order to find m we must divide both sides of the equation by 49.

Answer: The child's mass is 20.4 kg