CORC 1331 MAIN PAGE

PHYSICS TOPICS

Speed
Velocity
Acceleration
Constant Acceleration
Free Fall
Forces and Newton's Law
Kinetic Energy
Potential Energy

LIST OF EXAMPLES

CLASSIC PROBLEMS

Free Fall
Forces
Conservation of Energy
Conservation of Momentum

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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).

 Example 1: How to find the potential energy of an object if you are given the mass and height.

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.

 Example 2: How to find the height of an object if you are given the potential energy and mass.

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.

Cat sitting high up in a tree

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

50 J/117.6 = h
h =
0.43 m

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

 Example 3: How to find the mass of an object if you are given its potential energy and height.

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.

Girl running up a flight of stairs

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.

1000 J/ 49 = m
m =
20.4 kg

Answer: The child's mass is 20.4 kg