1. GRAVITATIONAL POTENTIAL & KINETIC ENERGY
Energy & Transformations
GRAVITATIONAL POTENTIAL & KINETIC ENERGY

2. Gravitational Potential Energy
The type of energy possessed by an object because of its height above ground.
Calculated by:
Units of GPE are Joules (J).
Where:
EG=Gravitational Potential Energy (J)
m = mass (kg)
h= height (m)

3. Example 1
Calculate the gravitational potential energy of a 15kg object 2.3m above the ground.

4. 1 G R F
m = 15 kg
h = 2.3m EG
EG = mgh S
∴ The object has a potential energy
of J

5. Kinetic Energy The type of energy due to an object’s motion.
Calculated by:
Units of Kinetic Energy are Joules (J).
Where:
EK= Kinetic Energy (J)
m = mass (kg)
v= velocity (m/s)

6. Example #2
What is the mass of a bullet traveling at 360 km/h with 750 J of kinetic energy?

7. 2 G R F EK = 750 J v = 360 km/h = 100 m/s m EK = ½mv2 S
∴ The bullet has a mass of 0.15kg

8. Mechanical Energy
The sum of gravitational potential energy and kinetic energy.
Law of conservation of energy:
“Energy cannot be created nor destroyed”.
Therefore:
Where 1 is the initial state, 2 is the final state.
*EM = Mechanical energy (J)

9. Example #3
What is the final speed of a ball, dropped from a height of 10 m?

10. 3 G R F h1 = 10m v2 EG = mgh EK = ½mv2 S
∴ The ball hits the ground with a
speed of 14 m/s.