1. Horses have it…
Mechanical Power

2. Definitions power: the rate at which… WORK IS DONE
ENERGY IS PRODUCED OR CONSUMED
unit: WATT
Equation

3. Example #1 – Power Plant
A power plant produces 300 mega joules of energy in 30 seconds. What is the power output of the plant?
P = W / t
P = 300 x 106 J / 30 s
P = 1 x 107 W (or 10 MW)
This means that the plant provides its customers with
10 million joules of energy every second
(Enough to keep standard light bulbs
continuously lit)

4. Example #2 – Dog Sled
A team of dogs pulls a sled with an average force of 3000 newtons across a distance of 200 meters in 75 seconds. What is their power output during this time?
P = Fd / t
P = (3000 N)(200 m) / 75 s
P = 8000 W (or 8 kW)

5. Example #3 – Elevator Motor
A motor pulls an 8000 newton elevator upward at an
average speed of 3.0 meters per second. What amount
of power is used by the motor?
How can the demand for power from the motor be
reduced?
P = Fv̄
P = (8000 N)(3 m/s)
P = 24,000 W
Pull the cars up at a slower speed or
Use lighter elevator cars.

6. End of PRACTICE