Another conservation of energy problem

1. Feb 22, 2009

physicsman2

1. The problem statement, all variables and given/known data
why is the gravitational potential energy of a ball equal to its kinetic energy

2. Relevant equations
KE=PE

3. The attempt at a solution
im really not sure, i think its because energy is conserved but i dont know why that is either

2. Feb 22, 2009

cybernerd

Yes, it has to do with the conservation of energy. Think of it this way - If you hold a ball in your hand and drop it, the kinetic energy will equal the gravitational potential energy, because the ball cannot acquire energy from any other source. Gravity is the only thing pulling the ball down - no other force is going to help the ball fall.

3. Feb 22, 2009

physicsman2

oh i understand now thanks

4. Feb 22, 2009

LowlyPion

As stated it is not.

The conservation of energy tells you however that the Δ in potential energy will manifest as a Δ in kinetic energy when a ball is released in a gravitational field.