Physics Form 3 Question Paper

Physics Form 3

Course:Physics

Exam Year:2008

Physics Form 3

Answer all questions.

1. Sketch a diagram showing how a bunsen burner can be placed on a table in each of the following states of equilibrium (3mks)

i. Neutral.
ii. Stable
iii. Unstable

2. State the effect of a decrease in temperature on surface tension (1mk)

3. Why is concrete reinforced with steel in constructing beams? (3mks)

4. On a frosty day, the metal handlebars of a bicycle feel colder than the rubber grips. Explain (2mks)

5. State two facts which show that heat from the run does not reach the earth's surface by convection (2mks)

6. Explain why plants in green house experience higher temperatures than the ones outside (2mks)

7. The size of the pinhole camera is increased. State and explain what happens to the images (2mks)

8. Name two advantages which a lead-acid accumulator has over a dry cell (2mks)

9. Using the domain theory, explain why a magnet may lose its magnetism by heating or hammering (3mks)

10. You are provided with the following apparatus; an illuminated object (candle), a rules, concave mirror, and a screen.
With the aid of a labelled diagram, explain carefully how you can determine the focal length of the mirror (8mks)

11. Give a reason why an object with a narrow base topples easily than one with a wide base (2mks)

12. State one reason why in construction of car head lamps parabolic reflectors are preferred to spherical reflectors (1mk)

13. (a) What is the difference between a hard magnetic material and a soft magnetic material (2mks)

b. Give two ways in which the strength of an electromagnet can be increased (2mks)

14. (a) State Hooke's law (1mks)

b. A force of 7.5N stretches a certain spring by 5.0cm. How much work is done in stretching this spring by 8.0cm? (4mks)

15. (a) Define the following terms:
i. Wavelength (1mk)
ii. Frequency (1mk)
iii. Period (1mk)

b. In which ways do mechanical waves and electromagnetic waves differ (2mks)

c. Give one example of each of the following types or forms of waves.
i. Longitudinal (1mk)
ii. Transverse (1mk)

16. A bullet is fired horizontally at a target, neglecting air resistance, give a reason why the horizontal acceleration of the bullet is zero (1mk)

17. A car of mass 1000kg travelling at 36km/h is brought to rest over a distance of 20m. Find:

i. Acceleration (3mks)

ii. The breaking force (2mks)

18. (a) State three factors that affect speed of lights in air (3mks)

b. A mine worker stands in between two cliffs. The cliffs are X metres apart. Each time he strikes the rocks once,he hears two echos; the first one after 25 seconds and the one follows 2 seconds later. Calculate;

i. The velocity of sound in air (3mks)
ii. The value of X (4mks)

19. A beaker of height 10cm is filled with water. An optical pin which is at the bottom of the beaker is then viewed from the top of the beaker. How far does the pin appear from the surface? (refractive index of glass= 1.495)
(3mks)

20. A rifle of mass 4.0 kg fires a bullet of mass 12.0g with a nozzle velocity of 700m/s. Assuming that the rifle is free to move, find the velocity of recoil (3mks)

21. A machine with a wheel diameter of 1.2m and an axle of diameter 0.4m lifts a load of mass 9kg with an effort of 100N. Given that the acceleration due to gravity is 10m/s2, calculate:

i. The velocity ratio of the machine (3mks)

ii. The mechanical advantage of the machine (2mks)

iii. The efficiency (2mks)

22. (a) A steel ball is dropped into a cylinder containing oil. Sketch a graph showing the variation of acceleration with time (3mks)

b. A motor uses an electrical energy at a rate of 200W and raises a mass of 25kg through a vertical distance of 20m in 0.5 minutes. What is the efficiency of the motor (3mks)

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