Gravitational Potential Energy 1

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Gravitational Potential Energy 1

If you drop a stone onto your feet from 5cm high, it would not hurt too much.
But if you you held the stone 2m above your feet, you can already anticipate the pain!
Whenever you raise an object above the ground, we say the object has gained Gravitational Potential Energy.
This name is given because it is gravity that is going to give it energy.
Greater heights gives the object greater Gravitational Potential Energy.

Some Facts
a. Gravitational Potential Energy is the energy an object has as a result of its height above the ground.
b. This energy is measured in joules (J)
c. It is a scalar quantity.
d. The symbol is E_p

GRAVITATIONAL POTENTIAL ENERGY FORMULA
The equation to calculate this energy is
E_p = mgh
E_p = Gravitational Potential Energy
m = mass of object
g = acceleration due to gravity (g = 10m.s^-2)
h = height raised above ground

Examples
1. A 4kg object is raised a height of 3m above the ground. Calculate its Ep.
E_p = mgh
E_p = (4)(3)(10)
E_p = 120J

2. The Ep of an 5kg object is 80J. Calculate the height to which it has been raised.
E_p = mgh
80 = 5(10)h
h = 1,6m

3. A stone is raised to 8m. It Ep is 200J. Calculate its mass.
E_p = mgh
200 = m(10)8
m = 2,5kg