Self-Test: Work, Energy and Power Test #1
Suggested Time: 45 minutes

1. A cyclist increases his kinetic energy from 1100 J to 5200 J in 12 s. His power output during this time is
 A. 92 W B. 260 W C. 340 W D. 430 W

2. What is the minimum power output of a small electric motor that lifts a 0.050 kg mass through 2.0 m in 30 s?
 A. 0.0017 W B. 0.017 W C. 0.033 W D. 15 W

3. A net force of 20 N acts for 1.5 s on a 4.0 kg object initially at rest. What is the final kinetic energy of the object?
 A. 30 J B. 110 J C. 230 J D. 440 J

4. The graph below shows how the force acting on an object varies with distance. What is the work done in moving the object from 20 m to 60 m?

 A. 50 J B.100 J C. 400 J D. 900 J

5. Two blocks are initially held together on a frictionless surface as shown in the diagram below. When the string is cut, the blocks fly apart as shown. What work was done on the blocks by the spring?

 A. 0 J B. 0.29 J C. 0.43 J D. 0.58 J

6. Which of the following is a definition of power?

A. Power is the rate of change of flux.

B. Power is the rate of change of energy.

C. Power is the rate of change of momentum.

D. Power is the rate of change of displacement.

7. René, whose mass is 85 kg, skis down the hill, passing Z with a kinetic energy of 9700 J. If friction is ignored, to what maximum height, h, can René ski?

 A. 12 m. B.15 m C. 1.1 x 102 m D. 6.6x 102 m

8. A cyclist travelling at 10 m/s applies her brakes and stops in 25 m. The graph shows the magnitude of the braking force versus the distance travelled. What is the total mass of bike and cyclist?

 A. 20 kg B. 40 kg C. 64 kg D. 80 kg

9. Calculate the minimum power of a cyclist who can increase his kinetic energy from an initial value of 480 J to a final value of 2430 J by travelling 26 m in 4.0 s.
 A. 75 W B. 3.6 x 102 W C. 4.9 x 102 W D. 7.3 x 102 W

10. As a skier descends a slope, her kinetic energy increases from 600 J to 3200 J while her gravitational potential energy decreases by 5900 J. How much heat energy is created due to friction?
 A. 2100 J B. 3300 J C. 8500 J D. 9700 J

11. A 60 kg girl and her 45 kg brother are at rest at the centre of a frozen pond. He pushes her so that she slides away at 2.4 m/s. How much total work is done? (Ignore friction.) A. 58 J B. 170 J C. 350 J D. 400 J

12. How much work must be done to stop an 1800 kg vehicle travelling at 30 m/s?
 A. 1.8 x 104 J B. 5.4x 104 J C. 5.3x 105 J D. 8.1 x 105 J

13. A basketball is thrown into the basket, as shown in the diagram below. The ball leaves the player's hand at t = 0 s and reaches the basket at t = 3 s. Which of the following graphs best represents the ball's kinetic energy Ek as a function of time? 14. A 0.030 kg toy car is pushed back against a spring-based launcher as shown in Diagram 1. Diagram 2 shows a graph of the force required to compress the spring 0.090 m. a) What is the work done in compressing the spring? (3 marks)

b) Assuming no losses due to heat, what maximum speed is reached by the toy car when it is released? (3 marks)

c) If in fact the maximum kinetic energy of the car is 0.18 J , what is the efficiency of the spring-based launcher? (1 mark)

15. A 150 kg roller coaster car passes the crest of a hill at 15.0 m/s. a) What is the speed of the car at point B at the bottom of the hill? Consider friction forces negligible. (5 marks)

b) If the mass of the roller coaster car is increased by adding a passenger, how will the speed at B now compare to your answer for part a)? (Circle one.) (1 mark)

A. equal to

B. less than

C. greater than

16. As a 62 kg skier descends from A to B her velocity increases from 8.5 m/s to 23.3 m/s. Friction between A and B generates 8700 J of heat energy. Through what vertical height, h, did the skier descend? (7 marks) Back to Self-Test Menu