CALCULATING POWER
Name: Date:
Use this worksheet to get extra practice doing the calculations in Math Connect: Using a Formula to Calculate Power.
- Follow the steps outlined in your textbook.
- Use a calculator to do the calculations.
Equation
power = or P =
Solve These
1. An instrument uses a battery that provides 500 J of energy for 1200 seconds. What is the power of the instrument?
What do you know?
power = ____; energy = ____; time = ____
equation to use = ______
What do you want to find out? ______
Use the formula.
P = =
State the power in watts. ______
2. A chainsaw used 4000 J in 180 s. Calculate the power used, in watts.
What do you know?
power = ____; energy = ____; time = ____
equation to use = ______
What do you want to find out? ______
Use the formula.
P = =
State the power in watts. ______
CHAPTER 6 /BLM 6–9
REINFORCEMENT /Calculating Power (continued)
3. A diver used 6000 J to dive off a rock cliff. If the diver took 2.5 seconds to reach the water, how much power was used?
What do you know?
power = ____; energy = ____; time = ____
equation to use = ______
What do you want to find out? ______
Use the formula.
P = =
State the power in watts. ______
4. A battery uses 900 J of energy to run a radio for 25 minutes. What is the power, in watts, of the radio? Hint: Change the 25 minutes to seconds.
What do you know?
power = ____; energy = ____; time = ____
Convert time to seconds:
equation to use = ______
What do you want to find out? ______
Use the formula.
P = =
State the power in watts. ______
Extend Your Skills
5. Rearrange the formula to calculate energy. If a portable phone needs two watts to operate and it is used for 15 seconds, how many joules will have been used?
What do you know?
power = ____; energy = ____; time = ____
Rearrange the P = formula to calculate energy. ______
What do you want to find out? ______
Use the formula.
State the energy in joules. ______
CHAPTER 6 /BLM 6–10
REINFORCEMENT /Calculating Watt Hours
Name: Date:
Use this worksheet to get extra practice doing the calculations in Math Connect: Watt Hours.
- Follow the steps outlined in your textbook.
- Use a calculator to do the calculations.
Equation
Energy = Power x time orE = P•t
Solve These
1. An instrument uses 250 000 W in two hours. What is the energy used, in watt hours?
What do you know?
energy = ____; power = ____; time = ____
equation to use = ______
What do you want to find out? ______
Use the formula.
State the energy in watt hours. ______
2. A machine uses 5 000 W in three hours. How much energy was used?
What do you know?
energy = ____; power = ____; time = ____
equation to use = ______
What do you want to find out? ______
Use the formula.
State the energy in watt hours. ______
CHAPTER 6 /BLM 6–10
REINFORCEMENT /Calculating Watt Hours (continued)
3. A small toy uses 50 W in half an hour. How much energy was used, in watt hours?
What do you know?
energy = ____; power = ____; time = ____
equation to use = ______
What do you want to find out? ______
Use the formula.
State the energy in watt hours. ______
4. A 100 W light bulb is left on for 24 hours. How much energy was used, in watt hours?
What do you know?
energy = ____; power = ____; time = ____
equation to use = ______
What do you want to find out? ______
Use the formula.
State the energy in watt hours. ______
Extend Your Skills
5. A battery produces 25 W in 60 seconds. How much energy was used, in watt hours? Hint: Convert the 60 seconds to hours before doing the calculations.
What do you know?
energy = ____; power = ____; time = ____
Convert time to hours:
equation to use = ______
What do you want to find out? ______
Use the formula.
State the energy in watt hours. ______
BLM 6–11
REINFORCEMENT /Calculating Kilowatt Hours
{AB.Sc24.B.K.2.v}{AB.Sc24.B.S.2.ii}{AB.Sc24.B.S.2.i}
Name: Date:
Use this worksheet to get extra practice doing the calculations in the Math Connect: Calculating Kilowatt Hours.
- Review the steps outlined in your textbook.
- Fill in the equation and how to convert W•h to kW•h in the space provided.
- Use the steps to help you identify what calculations to do for columns 4 and 5 in the table below.
- Use a calculator to do the calculations.
- When you have completed your calculations, total the amounts in column 5 to determine how many kilowatts all of the appliances use together in one month. If you are not using a calculator, make sure you line up your answers so the decimals are directly beneath each other. Write the total in the bottom box in column 5.
- Consider the Think About It question that follows. Discuss your ideas with a group. Write some suggestions in the table provided on the next page.
Equation
What equation do you need to calculate energy? ______
What equation do you need to change W•h to kW•h? ______
Appliance / Power Rating (W) / Average Number of Hours Used in a Month / Energy Usedin a Month (W•h) / Energy Used
in a Month
(kW•h)
tabletop fan / 240 / 10 / 240 x 10 = 2400 / = 2.4
dishwasher / 1500 / 45
clothes dryer / 2185 / 90
colour television / 255 / 45
stereo / 100 / 60
car block heater / 600 / 72
total kilowatt
hours (kW•h)