1. Power Power The rate of doing work Watts Power Generation Stations
Check Your Understanding
Horsepower

2. Power
The rate of doing work or transforming energy
It is a scalar quantity
The unit for energy is the joule
Since we are discussing a rate it must be over a time period (seconds)
Power is therefore measured in J/s
1 J/s = 1 watt (W)
since E = Wnet
P = E t
P = Wnet t

3. Watts
Watts (W) and kilowatts (kW) are commonly used to indicate the power of electrical appliances
How much power they consume per second of operation

4. Watts
Megawatts and Gigawatts are often used to rate the power of electric generating stations.
This rating indicates how much energy the station generates per second
Example: The coal-fired Ratcliffe Power Station in the UK has a rated capacity of 2 gigawatts (2000 Megawatts).

5. Check Your Understanding
A 51-kg student climbs 3.0 m up a ladder in 4.7 s. Calculate the student’s
gravitational potential energy at the top of the climb.
power for the climb.
Answer: a) 1.5 x 103 J b) 3.2 x 102 W

6. Check Your Understanding
A 85 kg man climbs from a height of 2900 m to 3640 m in 60 minutes. What is the man’s average power?
Answer: 1.7 x 102 W

7. Check Your Understanding
The power rating of the world’s largest wind generator is 3.0 MW. How long would it take such a generator to produce 1.0 × 1012 J, the amount of energy needed to launch a rocket, in days?
Answer: 3.9 days

8. Check Your Understanding
The nuclear generating station located in Pickering, Ontario is rated at 2160 MW of electrical power output. How much electrical energy, in megajoules, can this station produce in one day?
Answer: 1.87 x 108 MJ

9. Check Your Understanding
The Lamborghini Murcielango LP670-4 SuperVeloce has a weight of 3,450 lbs and can go from 0.0 – 60.0-mph in 2.8 seconds. What is the average power output of the cars engine in kW?
Answer: 201, W = kW = 2.0 x 102 kW

10. Horsepower Is a unit of measurement for power 1 W = 0.00134 horsepower
1 kW = 1.34 horsepower
Looking at the previous question, what is the cars horsepower?
Power = ?
P = kW x 1.34 hp = 269 hp
1 kW