1. Potential Energy

2. Potential Energy
Energy associated with forces that depend on the position or configuration of a body
Objects acquire potential energy when work is done on it
As an object loses potential energy, it can do work

3. Potential energy is the capacity to do work even if not doing work yet
Potential energy can be stored for later use
Equal to the negative of the work done on it to give it this potential energy to begin with

4. Gravitational Potential Energy
Potential energy because of an object’s position relative to the Earth
W = Fdcosθ
To give an object PE it must be worked on as it is lifted to a height (h)
The force to lift it is equal to the force of gravity on it (mg)
W = mghcosθ
Since θ is zero, W= mgh

5. Gravitational Potential Energy
PEG = mgy y- height above reference
WG = -mg(y2 – y1) = - ΔPE
The initial reference point doesn’t matter, it is the change in PE that matters

6. Example 1
A 1000kg roller coaster car moves from pt 1 to 2 and then to 3. A) what is the PE at 2 and 3 relative to 1? B) What is the ΔPE when it goes from 2 to 3? C) Repeat part A and B relative to point 3.