PHYSICS QUESTIONS AND ANSWERS (3)

1. The efficiency of a machine is always less than 100% because the
   A. work output is always greater than the work input
   B. load lifted is always greater than the effort applied
   C. effort applied is always greater than the load lifted
   D. velocity ratio is always greater than the mechanical advantage
2. In the J-tube above, Y and X are on the same horizontal level and 30cm3 of air is trapped above Y when the atmospheric pressure is 75cm Hg, calculate the volume of air trapped above Y when 15cm Hg is now poured into the limb above X
   A. 15 cm3 B. 25 cm3 C. 35 cm3 D. 45 cm3
3. The diagram above shows the force-extension curve of a piece of wire. The energy stored when the wire is stretched from E to F is
   A. 7.5 x 10-3J B. 2.5 x 10-3J
   C. 1.5 x 10-2J D. 7.5 x 10-1J
4. The diagram above shows the force (F) acting on an object through a distance (x). The work done on this object is expressed as
   A. Fx J B. Fx/2 J C. Fx2 J D. F/x J
5. Water does not drop through an open umbrella of silk materials unless the inside of the umbrella is touched. This is due to
   A. capillarity
   B. osmotic pressure
   C. viscosity
   D. surface tension
6. The stylus of a phonograph record exerts a force of 7.7 x 10-2N on a groove of radius 10-5m. Compute the pressure exerted by the stylus on the groove
   A. 2.45 x 108 Nm-2 B. 3.45 x 108 Nm-2
   C. 4.90 x 108 Nm-2 D. 2.42 x 108 Nm-2199
7. A machine whose efficiency is 60% has a velocity ratio of 5. If a force of 500N is applied to lift a load P, what is the magnitude of P?
   A. 1500N B. 500N
   C. 4166N D. 750N
8. In a hydraulic press, a force of 40N is applied on the effort piston of area 0.4m2. If the force exerted on the load piston is 400N, the area of the large piston is
   A. 4m2 B. 8m2 C. 2m2 D. 1m2259
9. As the pressure of a fluid increases, its viscosity
   A. decreases
   B. increases
   C. increases then decreases
   D. remains constant
10. The process whereby the molecules of different substances move randomly is called?
    A. capillarity
    B. surface tension
    C. osmosis
    D. diffusion
11. The terminal velocity of a ball-bearing falling through a viscous fluid reached when the
    A. upthrust is equal to the weight of the ball
    B. ball accelerate uniformly
    C. upthrust is equal to the velocity of the ball
    D. velocity is uniform
12. An empty density bottle weighs 2 N. if its weighs 5 N when filled with water and 4 N when filled with olive oil, the relative density of olive oil is
    A. 1/3 B. 2/3 C. 1/5 D. 2/5
13. If a heavy barrel is rolled up a plane inclined at 30° to the horizontal. its velocity ratio will be
    A. 3.0 B. 3.1 C. 3.2 D. 2.0424
14. I. Density of the liquid.
    II. Acceleration due to gravity.
    III. Type of container of the liquid.
    IV. The constituents of the liquid.
    Which of the above conditions will NOT affect the pressure of fluid?
    A. I and III only
    B. II and III only
    C. III and IV only
    D. I and II only
15. A machine of velocity ratio 6 requires an effort of 400N to raise a load of 800N through 1m. Find the efficiency of the machine
    A. 55. 6 % B. 50.0%
    C. 33.3% D. 22.2%469
16. If a wire 30 cm long is extended to 30.5 cm by a force of 300 N. find the strain energy of wire
    A. 0.75 J B. 7.50 J
    C. 75.00 J D. 750.00 J
17. In a hydraulic press, the pump piston exerts a pressure of 100Pa on the liquid. What force is exerted in the second piston of cross-sectional area 3 m2?
    A. 300 N B. 200 N C. 150 N D. 100 N
18. An object weighs 22 kg in water and 30kg in air. what is the upthrust exerted by the liquid on the object. [g = 10 ms2]
    A. 50 N B. 520 N C. 220 N D. 80 N
19. A copper wire was subjected to a tensile stress of 7.7 x 107 Nm-2. Calculate strain of the wire.
    [Young’s modulus = 1.1 x1011Nm-2]
    A. 2. 0 x 10-5 B. 7.0 x 10-3
    C. 7.0 x 10-4 D. 2.2 x 10-4
20. A piece of cork floats in a liquid. What fraction of its volume will be immersed in the liquid?
    [Density of the cork = 0.25 x 103kgm-3, Density of the liquid = 1.25 x 103kgm-3]
    A. 0.8
    B. 0.5
    C. 0.2
    D. 0.1

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ANSWERS

1. D

2. B

3. B

4. B

5. D

6. A

7. A

8. A

9. B

10. D

11. D

12. B

13. D

14. C

15. C

16. A

17. A

18. D

19. C

20. C