1. CHAPTER 15:
ENERGY!

2. Energy: Measured in joules!
The ability to do work
Work = Force x distance
Measured in joules!

3. ENERGY

4. Forms of Energy: Kinetic: energy of movement (depends on
mass and velocity)

5. Forms of Energy: Potential: energy of position
- gravitational: depends on mass, height
and acceleration due to gravity
- elastic: depends on ability to be
stretched or compressed
- chemical: stored in bonds
- electrical: associated with charge
- nuclear: stored in the atomic nucleus
- electromagnetic: waves (light/rays/sound)

6. The Law of Conservation
of Energy
Energy is never created or destroyed – it is
transformed from one form to another.
(PE+KE)Beginning = (PE+KE)End

7. The Law of Conservation
of Energy
Often, kinetic energy will be transformed into
thermal energy, via FRICTION.
This is the reason we always LOSE efficiency
when work is done!

8. Calculating Kinetic Energy
m = mass (kg)
v = velocity (m/s)
KE = kinetic energy (Joules)

9. Calculating Kinetic Energy
What is the kinetic energy of a 75-kg student
running at a speed of 3 m/s?

10. Calculating Potential Energy
m = mass (kg)
g = acceleration due to gravity (9.8 m/s2)
h = height (m)
PE = potential energy (Joules)

11. Calculating Potential Energy
A mover carries a television with a mass of 62 kg
a distance of 18 m up the stairs. How much
potential energy does the TV have?
PE = (62)(9.8)(18)
= 10,937 J

12. The Law of Conservation
of Energy
If 2500-kg roller coaster car begins its descent from
500 m above the first hill, what is its kinetic energy at
the bottom of that hill?
PE = (2500)(9.8)(500) = 12,250,000 J = KE!