1. Types of Energy
Principles of Physics

2. Energy Objects have energy if they are able to do things
A way of explaining why things happen
Energy is a scalar quantity (no direction)

4. Kinetic energy Energy of Motion
KE = ½ mv2 KE = Kinetic energy (Joules = J)
m = mass (kg)
v = velocity (m/s)

5. Example
A 5 kg block is sliding on a frictionless horizontal surface with a speed of 5 m/s. Calculate the kinetic energy of the block
KE = ½ mv2
= ½ (5)(5)2
KE = 62.5 J

6. Potential energy Energy of position or condition
Gravitational PE = mgh
PE = potential energy (J) m = mass (kg)
g = gravitational acceleration
= 9.8 m/s2
h = height (m)
Other types of PE: spring, electrostatic

7. Example
A 0.100kg egg is dropped from the top of the bleachers which are 5.5 m high. Calculate the potential energy of the egg.
PE = mgh
PE = (0.100)(9.8)(5.5)
PE = 5.39 J

8. Mechanical energy Total mechanical energy of a system:
All the potential energy and all of the kinetic energy that the system contains

9. Example
A toy airplane with a mass of 30 kg is travelling 35 m above the ground at 40 m/s. How much mechanical energy does the airplane have? KE = ½ mv2 PE = mgh KE = ½ (30)(40)2 PE = (30)(9.8)(35) KE = 24,000 J PE = 10,290 J Total Mechanical Energy = 24, ,290 = 34,290 J