# What do we call these energy forms?

First of all I apologize for the basic question.

When we throw a ball upwards, energy gets converted from us to kinetic energy which becomes potential energy and as the ball falls back down it becomes kinetic energy once again while falling down.

So I have 2 questions

1. What do we call the energy form that originates from us, i.e. that we convert into the kinetic energy of the ball in the first place

2. What are the main conversions of energy as the ball comes to a stop?

• For 1), you store energy in your body as ATP, so you may want to look at how ATP is capable of storing energy, which essentially has to do with a bond. There are a lot of complex processes that occur to go from ATP to your muscles throwing the ball. – JamalS Mar 3 '18 at 21:42

## 2 Answers

1) There are many types of potential energy. You could think of your arm as sort of like a spring, which stores elastic potential energy. More accurately it would be chemical potential energy that helps the muscles contract which comes from eating food which contains energy from solar radiation.

2) As the ball comes to a stop all the energy turns into heat & sound.

• I would also add a small change in the Earth's kinetic energy to your answer to #2. – probably_someone Mar 4 '18 at 2:19

This is fairly standard question with fairly standard answer. We use chemical energy stored in the food we eat to supply the ball with kinetic energy.

When we let go of the ball, its kinetic energy is at a maximum and its potential energy is at a minimum. When the ball is at its highest point its kinetic energy as at a minimum (zero) and its potential energy is at a maximum. This then reverses again when the ball falls back down.

All points in between the energy of the ball is the addition of its potential and kinetic energy's, as energy is conserved and only lost to "frictional" forces acting on the ball. For example a ball will go higher in an airless environment, also the falling ball does not reach a "Terminal velocity" that would skew our calculations.