1. Chapter 5.2

2. Energy
 The ability to do work
 Any object that has energy has the ability to create
force to do work
 Energy is measured in the same units as work
 Unit – joule(J)

3. Forms of Mechanical Energy
1. Kinetic Energy
 Energy in the form
of motion
Ex) A spinning
bicycle wheel
Ex) Sprinting runners
2. Potential Energy
 Stored Energy –
not moving
Ex) A drawn bow
Ex) A book on the top
shelf
Ex) A stretched
rubber band

4. Potential Energy
 Depends on its
position above the
ground
 The greater the
height, the greater
the PE
 Examples
 Gravitational potential
energy (g)
 Elastic potential
energy

5. Potential Energy
Ep = mgh
Height (m)
Potential Energy (J)
Acceleration
of gravity (m/sec2)
Mass (kg)

6. Kinetic Energy
 The greater the mass
the more KE
 The greater the velocity
the greater the KE
 Here the green particle
is moving twice as fast
as the yellow particle. It
has more kinetic energy
than the yellow one.

7. Kinetic Energy
Ek = ½ mv2
Speed (m/sec)
Kinetic Energy (J)
Mass (kg)

8. Mechanical Energy
 Equals the total amount of KE and PE in a
system
 Mechanical Energy = KE + PE

9. Law of Conservation of Energy
 Energy can never be created nor destroyed its
transformed into another energy

10.  Total energy can never exceed starting energy
(it should always be equal)
 KE converted to PE and back
 Friction slows objects down