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 60% of the power a winch draws goes into lifting. It raises a 3 kg crate 5 m in 5 s at steady speed. What power does it draw, Bo?

   49 W
3. 3.

   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
5. 4.

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

   • 240 W, the work at 4 s
   • 60 W
   • 960 W, the work times the time
6. 5.

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

   Use the picture in question 4.

   • 50 W, the 300 J split over 6 s
   • 10 W
   • 30 W, the average over the whole run
7. 6.

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

   Use the picture in question 4.

   • 10 W, the final slope
   • 35 W, the mean of the two slopes
   • 30 W
8. 7.

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

   • 0.5 kWh
   • 1.2 kWh
   • 30 kWh
   • 0.048 kWh
9. 8.

   A 60 W bulb and a 9 W LED give the same light. Both run 5 h a day. How much energy does the LED save each day, Noah?

   • 51 Wh
   • 255 Wh
   • 45 Wh
   • 300 Wh
10. 9.

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

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

11. 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

12. 10.

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

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