1. The Work Energy Principle part 3
By Heather Britton

2. Energy of Motion
Aside from potential energy, there is also energy of motion
The energy of motion is called kinetic energy
Kinetic is a Greek word for motion
There is a formula to determine a moving objects kinetic energy

3. Derivation of the Kinetic Energy Formula
Recall ΔE = W = FΔx
F = ma
a = (v - v0)/t
vavg = (v + v0)/2
Δx = vavgt
KE = (1/2)mv2

4. Kinetic Energy KE = (1/2)mv2 The v2 is very important conceptually
If one object has twice the velocity of an equal mass object it has 4 times the kinetic energy
Three times as fast equals 9 times the kinetic energy

5. Example 7
A kg dart leaves a toy gun with a velocity of 11.2 m/s. What is the kinetic energy of the dart?
Answer
12.5 J

6. Practice