1. Forms of Energy
Mechanical energy is the energy possessed by an object due to its motion or its position.
Radiant energy includes light, microwaves, radio waves, x-rays, and other forms of electromagnetic waves.
Nuclear energy is released when heavy atoms in matter are split up or light atoms are put together.
The electrical energy we use is derived from other sources of energy.

3. Kinetic Energy Energy of motion is called kinetic energy.
The kinetic energy of a moving object depends on two things: mass and speed.
Kinetic energy is proportional to mass.

4. Kinetic Energy
Mathematically, kinetic energy increases as the square of speed.
If the speed of an object doubles, its kinetic energy increases four times. (mass is constant)

5. Kinetic Energy KE = 1 mv2 2 Mass (kg) Kinetic Energy Speed (m/sec)
(joules)
KE = 1 mv2 2
Speed (m/sec)

6. Kinetic Energy
Kinetic energy becomes important in calculating braking distance.

7. Calculate Kinetic Energy
A car with a mass of 1,300 kg is going straight ahead at a speed of 30 m/sec (67 mph).
Calculate:
a) The kinetic energy of the car.
1) You are asked for the kinetic energy and stopping distance.
2) You are given mass, speed, and the force from the brakes.
3) Kinetic energy Ek = 1/2 mv2 Work, W = Fd
4) Solve:
Ek = (1/2)(1,300 kg)(30 m/sec)2 = 585,000 J
To stop the car, the kinetic energy must be reduced to zero by work done by the brakes.
585,000 J = (9,500 N) × d d = 62 meters

8. Examples
Determine the kinetic energy of 625kg roller coaster car that is moving with a speed of m/s.

9. Problem
Miss Diwater, the former platform diver for the Ringling Brother’s Circus, had a kinetic energy of 12,000. J just prior to hitting the bucket of water. If Missy’s mass is 40.kg, then what is her speed?

10. YOU TRY!
Pg. 174 # 1-5

11. Work-Kinetic Energy Theorem
Wnet = ΔKE Or
Wnet = 1/2mVf2 – 1/2mVi2
Net work = change in kinetic energy

12. Example
On a frozen pond, a person kicks a 10.0 kg sled, giving it an initial speed of 2.2m/s. How far does the sled move coming to a complete stop if the coefficient of kinetic friction between the sled and the ice is 0.10?

13. YOU TRY
Pg #1+2