Page 227 - Physics

Work, energy and power

much work is done in moving the Section B
car up the hill? 3. (a) Defi ne the term work.

(a) 50×10 J (b) What happens to work done
3
(b) 5.0 10 J 3 when force and displacement
are in the same direction?
(c) 1.0 10 J 5 (c) What happens when force and

(d) 1.0 10 J 6 displacement are in opposite
directions?
(x) Which one of the following equations 4. (a) Defi ne the term power.
shows the relationship between (b) How is power measured?
power and work done? (c) Express 6 900 J/s in horsepower.
work done 5. Explain why a rotating wonder wheel
(a) power = time taken becomes hot after a sudden stop.

work done 6. Calculate the work done in each case
(b) power = distance moved below. Indicate if the work is done
on the object or by the object.
(c) power work done time taken  (a) A 10 kg object is lifted to a
(d) power work done velocity  height of 5 m above the ground.

2. Match each item from Column (b) The object is held at a height of
A with its corresponding item in 5 m for 7 s.
Column B. Then, write the letter (c) The object is lowered back to
of the correct response in the space the ground.
provided. 7. A motor exerts a horizontal force of

Column A Answer Column B 200 N in pulling a box 10 m across
i. 1 kW A. Motion in upward a level fl oor. How much work does
ii. Horse or downward the motor do?
power B. 1 000 W 8. An object is dropped and falls to
iii. PE C. kgm /s 2 the ground. Is there any work done
2
iv. Joule D. Motion parallel to while it is falling? If so, what force
v. Watt force is responsible? Is the work done on
E. Mechanical energy or by the object?
F. 750 W 9. A 1 000 kg car is travelling down
G. SI unit of power the road at a speed of 15 m/s. How

1 2 much kinetic energy does it have?
H. 2 mv 10. A 1 000 kg car travelling at 15 m/s
I. SI unit of energy has its speed increased to 45 m/s.
J. 746 W How much kinetic energy would it
have? How many times greater is

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Physics Form 1 Final.indd 221 16/10/2024 20:58