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 = energy E or P = time t 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. E P= = t 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. E P= = t State the power in watts. ___________________________________________________ CHAPTER 6 REINFORCEMENT BLM 6–9 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. E P= = t 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. E P= = t 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 = ____ E formula to calculate energy. ____________________ t What do you want to find out? Rearrange the P = ______________________________________________ Use the formula. State the energy in joules. _________________________________________________ CHAPTER 6 REINFORCEMENT BLM 6–10 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 or E = 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 REINFORCEMENT BLM 6–10 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. ______________________________________________ CHAPTER 6 REINFORCEMENT BLM 6–11 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 tabletop fan 240 Average Number of Hours Used in a Month 10 dishwasher 1500 45 clothes dryer 2185 90 colour television 255 45 stereo 100 60 car block heater 600 72 total kilowatt hours (kW•h) Power Rating (W) Energy Used in a Month (W•h) 240 x 10 = 2400 Energy Used in a Month (kW•h) 2400 = 2.4 1000