- Definition 1: Mechanical energy
Mechanical energy is the sum of the gravitational potential energy and the kinetic energy of a system.
Quantity: Mechanical energy () Unit name: Joule Unit symbol: J
Mechanical energy, , is simply the sum of gravitational potential energy () and the kinetic energy (). Mechanical energy is defined as:
You may see mechanical energy written as U. We will not use this notation in this book, but you should be aware that this notation is sometimes used.
Example 1: Mechanical energy
Calculate the total mechanical energy for a ball of mass 0,15 kg which has a kinetic energy of 20 J and is 2 m above the ground.
Analyse the question to determine what information is provided
The ball has a mass kg
The ball is at a height m
The ball has a kinetic energy J
Analyse the question to determine what is being asked
We need to find the total mechanical energy of the ball