Power

Answer Key - Grade 11 Science Worksheet - Building Confidence

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

1. 1.

   Only 35% of the power a winch draws goes into lifting. It raises a 5 kg crate 4 m in 4 s at steady speed. What power does it draw, Ari?

   140 W
2. 2.

   Only 80% of the power a winch draws goes into lifting. It raises a 4 kg crate 10 m in 5 s at steady speed. What power does it draw, Esme?

   98 W
4. 3.

   In the work-time graph, what is the motor's power during the first 4 s, Jun?

   • 960 W, the work times the time
   • 240 W, the work at 4 s
   • 60 W
5. 4.

   In the work-time graph, what is the motor's power from 4 s to 10 s, Kira?

   Use the picture in question 3.

   • 50 W, the 300 J split over 6 s
   • 30 W, the average over the whole run
   • 10 W
6. 5.

   In the work-time graph, what is the motor's average power over all 10 s, Luz?

   Use the picture in question 3.

   • 35 W, the mean of the two slopes
   • 30 W
   • 10 W, the final slope
7. 6.

   A 1.2 kW toaster oven runs for 25 minutes. How much energy does it use, Milo?

   • 30 kWh
   • 0.048 kWh
   • 0.5 kWh
   • 1.2 kWh
8. 7.

   A 2,000 W kettle runs for 3 minutes. How many joules does it use, Pia?

   • 100 J
   • 360,000 J
   • 360 J
   • 6,000 J

9. Read this first

   Machine tests (example data)

   Machine	Work done (kJ)	Time (s)
   A	0.9	6
   B	2.4	20
   C	0.3	3
   D	1.6	8

10. 8.

    Using the table, which machine has the most power, Ren?

    • Machine D, at 200 W
    • Machine A, at 150 W
    • Machine C, which takes the least time
    • Machine B, which does the most work
11. 9.

    Machine B keeps its power steady for 5 minutes. How much work does it do, Tala?

    • 720 kJ
    • 12 kJ
    • 0.6 kJ
    • 36 kJ
12. 10.

    How many times the power of machine C is machine D's, Zee?

    • 2.7 times
    • 0.5 times
    • 5.3 times
    • 2 times