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11th grade Power worksheet

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Power

Grade 11 Science Worksheet - Challenge Me

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Circle the best answer, or write your answer on the line.

  1. A turbine must deliver 98000 W of electrical power from water falling 25 m. It is 80% efficient. How many kilograms of water must fall each second, Ari?

  2. A turbine must deliver 4900 W of electrical power from water falling 10 m. It is 40% efficient. How many kilograms of water must fall each second, Bo?

  3. A turbine must deliver 44100 W of electrical power from water falling 30 m. It is 75% efficient. How many kilograms of water must fall each second, Esme?

  5. In the power-time graph, how much energy does the motor deliver in all 10 s, Jun?

    • 735 J
    • 392 J
    • 686 J
    • 980 J

  6. In the power-time graph, the energy from the first 4 s lifts a 2 kg crate. How high does it rise, Luz?

    Use the picture in question 4.

    • 20 m
    • 35 m
    • 196 m
    • 10 m

  7. A pulley lets a 20 N pull raise a 100 N load, but the rope moves 5 times as far. Milo says a motor 5 times smaller can do it in the same time. Agree?

    • Agree: the pulleys supply the extra energy that the heavy load needs, so the motor can be smaller
    • Agree: a pull 5 times smaller needs a motor that is 5 times less powerful, whatever the rope does
    • Disagree: the rope is 5 times longer, so the motor needs 5 times more power to pull it
    • Disagree: the pull is 5 times smaller but the rope moves 5 times faster, so the power is the same

  8. Air draw a line is the only resistance on a car and grows as the square of its speed. Noah says driving half as fast halves the energy used per kilometer. Agree or disagree?

    • Agree: the trip takes twice as long, so the lower power is cancelled and the energy is halved
    • Agree: half the speed means half the power, so the energy used for each kilometer is half as much too
    • Disagree: power falls to an eighth, so the energy used for each kilometer falls to an eighth as well
    • Disagree: drag falls to a quarter, and energy per kilometer is drag times distance, so it falls to a quarter

  9. A lift must raise an 80 kg load 12 m in 20 s at steady speed. Its motor turns 70% of the power it draws into lifting. Which is the smallest rating that works, Ren?

    • 750 W
    • 600 W
    • 500 W
    • 1,000 W

  10. A 60 W motor turns 80% of its power into pulling. It pulls a 5 kg cart up a smooth 30° ramp at steady speed. How fast does the cart rise along the ramp, Tala?

    • 1.96 m/s
    • 2.45 m/s
    • 0.98 m/s
    • 3.06 m/s

  11. A winch lifts a load. A new job has a load twice as heavy, raised three times as high, in the same time. How does the power needed change, Zee?

    • 2 times as much
    • 6 times as much
    • 5 times as much
    • 3 times as much
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11th grade Power worksheet – printable
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About this worksheet

Power. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

  • I can find power as work ÷ time, P = W ÷ t, in watts (1 W = 1 J/s), and move between W, kW, J, kJ, s, minutes and kWh.
  • I can find the power a machine draws from the power it delivers and its efficiency, and the power a lift needs on a slope with friction.
  • I can use P = Fv at a steady speed, and say how power grows when speed, load or height changes.
  • I can read power as the slope of a work-time graph and energy as the area under a power-time graph, and judge claims about power.

Standard: none (TX, FL)

Words to know

power: How fast work is done: joules each second

watt (W): One joule each second

kilowatt (kW): 1000 watts

steady speed: Speed that doesn't change, so no energy goes into speeding up

slope: Rise ÷ run on a graph; on a work-time graph, the power

efficiency: Share of the power a machine draws that becomes useful work

kilowatt-hour (kWh): Energy used by 1 kW running for 1 hour: 3.6 million J

area under a graph: On a power-time graph, the area is the energy delivered

Common mistakes

Your child used the useful power and skipped the efficiency. A machine that wastes energy must draw more power than it delivers.

Your child multiplied by the efficiency instead of dividing. A motor always draws more power than it delivers.

Your child counted only the lift up the slope. The motor also works against friction over the same distance.

Questions parents ask

What is the most common mistake with power?

Your child used the useful power and skipped the efficiency. A machine that wastes energy must draw more power than it delivers.

Are these 11th grade science worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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