1. Chapter 13 Energy and Work Section 4 Power

2. Power Power is the rate at which work is done or the amount of work done in a unit of time. Power is the rate at which work is done or the amount of work done in a unit of time. When you know how fast work is done, you can calculate power. When you know how fast work is done, you can calculate power. Power is calculated by dividing the amount of work done by the amount of time taken to do the work. Power is calculated by dividing the amount of work done by the amount of time taken to do the work.

3. Power Power = Work / Time Power = Work / Time Or Or Power = Force X Distance / Time Power = Force X Distance / Time The unit of power is the joule per second (J/s) The unit of power is the joule per second (J/s) This unit is called the watt (W). This unit is called the watt (W).

4. Power Work is the transfer of energy. Work is the transfer of energy. Power is the rate at which energy is transferred from one object to another or converted from one form to another. Power is the rate at which energy is transferred from one object to another or converted from one form to another. For example, a 100-watt light bulb converts electrical energy to light and heat at a rate of 100 joules per second. For example, a 100-watt light bulb converts electrical energy to light and heat at a rate of 100 joules per second.

5. Power A crane lifts an 8,000 N beam 75 m to the top of the building in 30 s. How much power does the crane use? A crane lifts an 8,000 N beam 75 m to the top of the building in 30 s. How much power does the crane use? Power = Force X Distance / Time Power = Force X Distance / Time 8,000N X 75m / 30s = 8,000N X 75m / 30s = 600,000 Nm or 600,000J / 30s= 600,000 Nm or 600,000J / 30s= 20,000J/s or 20,000W or 20kW 20,000J/s or 20,000W or 20kW

6. Power A motor exerts a force of 10,000N to lift an elevator 6m in 5s. What is the power produced by the motor? A motor exerts a force of 10,000N to lift an elevator 6m in 5s. What is the power produced by the motor? 10,000N X 6m / 5s = 12,000W 10,000N X 6m / 5s = 12,000W

7. Power A tow truck exerts a force of 9,000N to pull a car out of a ditch. It moves the car a distance of 6m in 25s. What is the power of the tow truck? A tow truck exerts a force of 9,000N to pull a car out of a ditch. It moves the car a distance of 6m in 25s. What is the power of the tow truck? 9,000N X 6m / 25s = 2,160W 9,000N X 6m / 25s = 2,160W

8. Power The motor of electric fan converts 24,000J of electrical energy every minute (60s). What is the power of the fan’s motor? The motor of electric fan converts 24,000J of electrical energy every minute (60s). What is the power of the fan’s motor? 24,000J / 60s = 400J/s or 400W 24,000J / 60s = 400J/s or 400W

9. Power A 40 horsepower engine burns twice as much fuel each hour as a 20 horsepower engine. Explain this in terms of power and energy A 40 horsepower engine burns twice as much fuel each hour as a 20 horsepower engine. Explain this in terms of power and energy The 40 horsepower engine converts twice as fast as the 20 horsepower engine and it also produces energy twice as fast a 20 horsepower and has twice as much power as a 20 horsepower engine. The 40 horsepower engine converts twice as fast as the 20 horsepower engine and it also produces energy twice as fast a 20 horsepower and has twice as much power as a 20 horsepower engine.

10. Power Find the work you do when you exert a force of 40N to run a distance of 18 m in 4s. Then find the power you expend. Find the work you do when you exert a force of 40N to run a distance of 18 m in 4s. Then find the power you expend. Work = 40N X 18m = 720J Work = 40N X 18m = 720J Power= 720J / 4s = 180J or 180W Power= 720J / 4s = 180J or 180W