Physics 2011 JAMB Past Questions

1. A man standing on a lift that is descending does not feel any weight because

A. the inside of the lift is air tight
B. the lift is in vacuum
C. there is no reaction from the floor of the lift
D. there is no gravitational pull on the man in the lift

Correct Answer: Option C

Explanation

The resultant force acting on the man is given by w = mg - R
Mg - mg = 0
The man feels weightless because the reaction, R is equal to the weight mg

2. Two balls X and Y weighing 5 g and 50 kg respectively were throne up vertically at the same time with a velocity of 100 ms¹ .How will their positions be one second later?

A. X and Y will be 500 m from each other
B. Y will be 500 m ahead of X
C. X will be 500 m ahead of Y
D. X and Y both be 500 m from the poin of throw

Correct Answer: Option D

Explanation

v² = U² - 2G s
0 = 100² - 2 x 10 x s = 10000 - 20s
s = (10000)/20 = 500m
Which is independent of mass.the two bodies where acted upon by the same retarding force of gravity which is independent of mass of the body; therefore both will be 500 m from the point of throw.

3. If it takes an object 3s to fall freely to the ground from a certain height, what is the distance covered by the object?

A. 90 m
B. 30 m
C. 45 m
D. 60 m

Correct Answer: Option C

Explanation

S = (1)/2gt²
S = (1)/2 x (10)/1 x 3² =5 x 9 = 45 m

4. An object of mass 2 kg moves with a velocity of 10 ms¹ round at circle of radius 4 m. Calculate the centripetal force on the object

A. 25 N
B. 100 N
C. 50 N
D. 40 N

Correct Answer: Option C

Explanation

Centripetal force,
F =

\frac{m v^{2}}{r}

\frac{2 \times 10^{2}}{4}

\frac{200}{4}

= 50N

5. A carpenter on top of a roof of 20.0m high dropped a hammer of mass 1.5 kg and it fell directly to the ground. the kinetic energy of the hammer just before hitting the ground is?

[g = 10 ms^-2]

A. 600 J
B. 150J
C. 300 J
D. 450 J

Correct Answer: Option C

Explanation

K e just before hitting the gound
= P e at the maximum height (conservation of mechanical energy)
K e = P e = mgh = 1.5 x 10 x 20
= 300 J

6.If a tube of small radius opened at both ends is placed in a liquid, the liquid will

A. remain at the same level irrespective of whether the liquid wet the glass or not
B. fall below the liquid level if the liquid wets the glass
C. falls below the liquid level if the liquid does not wet the glass
D. rise above the liquid level if the liquid does not wet the glass

Correct Answer: Option C

Explanation

The liquid will rise up the capillary if it wets glass and falls below its wets glass and falls below its initial level if it does not wet glass

7. 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

Correct Answer: Option D

Explanation

upthrust = weight in air - weight in liquid = 30 x 10 - 22 x 10 = 300 - 220 = 80 N

8.A metal of volume 40 cm³ is heated from 30 °c to 90 °c, the increase in volume is

A. 0.12 cm³
B. 4.00 cm³
C. 1.20 cm³
D. 0.40 cm³
E. no correct option

Correct Answer: Option E

Explanation

increase in volume, DV = RV₁ ∆ θ = 3α Vsub>1 Dθ
= 3 x 2.0 X 10^-5 x 40 x (90 - 30)
= 6 x 10^-5 x 40 x 60
0.144 cm³
∴ No correct option

9. A copper wire was subjected to a tensile stress of 7.7 x 10⁷ x 10 Nm^-2. calculate strain of the wire.

[young modules = 1.1 x 10¹¹ Nm^-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

Correct Answer: Option C

Explanation

Young modules =

\frac{Tensile stress}{Tensile strain}

1.1 \times 10^{1} 1 = \frac{7.7 \times 10^{7}}{Tensile Strain}

∴ Tensile strain =

\frac{7.7 \times 10^{7}}{1.1 \times 10^{1} 1}

7.0 \times 10^{7 - 11} = 7.0 \times 10^{- 4}

I. High thermal capacity.
II. High sensitivity.
III.Easy readability.
IV. Accuracy over a wide range of temperature
From the statement above, the qualities of a good thermometer are

A. I and II
B. I, II,III and IV
C. I, III and IV
D. II, III and IV

Correct Answer: Option D

Explanation

A good thermometric liquid should not have a high thermal capacity so that the themperetue of the body being measured will not be affected
∴ II, III and IV are qualities of a good thermometer

11.A machine is used to lift a load of 20 N through a height of 10 m. if the efficiency of the machine is 40%, how much work is done?

A. 80 J
B. 500 J
C. 300 J
D. 120 J

Correct Answer: Option B

Explanation

Efficiency =

= 40 =

= 500J

I. Density of the liquid.
II. Depth below the surface of the liquid.
III. Surface area of the liquid.
In which of the statement above will pressure be dependent?

A. I and II only.
B. II and III only.
C. I, II and III only.
D. I and III only.

Correct Answer: Option A

Explanation

Pressure in liquid is independent of cross sectional area of the container/ liquid
∴ the correct options are I & II

13. Which of the following could be effectively used to reduce friction?

A. kerosene
B. grease
C. water
D. petrol

Correct Answer: Option B

Explanation

grease is more viscous than the rest of the liquids

14.Which of the following types of waves needs a medium for propagation?

A. sound waves
B. light waves
C. radio waves
D. x - rays

Correct Answer: Option A

Explanation

Sound is the only mechanical wave among the rest which are electromagnetic waves.

15. Which of the following electromagnetic waves has the highest frequency?

A. utra - violet rays
B. radio waves
C. x - rays
D. infrared - rays

Correct Answer: Option C

Explanation

r - rays has the highest frequency followed by X - rays, ultraviolet ray, visible light intra - red and the least is radio weaves

16. A perfect emitter or absorber of radiant energy is a

A. conductor
B. black body
C. white body
D. red body

Correct Answer: Option B

Explanation

Dull, black surface are good emitters or absorbers of energy

17. The ground is always cold at night because the

A. atmosphere absorbs the sun's energy at night
B. earth radiates heat to the atmosphere at night
C. sun no longer shine at night
D. atmosphere reflects the sun's energy at night

Correct Answer: Option B

Explanation

The earth radiate heat to the atmosphere at night thereby lowering the temperature of the ground

18. A cannon is fired from town X,after how long is the sound heard at a town Y 4.95 km away?

[velocity of sound in the air = 330 ms^-1]

A. 30 s
B. 10 s
C. 10 s
D. 15 s

Correct Answer: Option A

Explanation

V = (2X)/t
330 = (2 x 4.95 x 10³)/t
t = (9.9. x 10³/330 = (9900)/330 = (90)/3
= 30 secs

19. The phenomenon that shows that increase in pressure lowers the melting point can be observed in

A. sublimation
B. condensation
C. coagulation
D. regelation

Correct Answer: Option D

Explanation

Regelation means refreezing a phenomenon whereby melted ice free from increased pressure refreezed when they are released from the pressure.

20. A block of aluminum is heated electrically by a 30 w heater if the temperature rises by 10°c in 5 minutes, the heat capacity of the aluminum is

A. 900 JK^-1
B. 90 JK^-1
C. 100 JK^-1
D. 200 JK

Correct Answer: Option A

Explanation

Heat supplied = Heat gained Pt = MCDθ
30 x 5 x 60 = c x 10
where c = mc which is the heat capacity
c = (30 x 5 x60)/10 = 900 JKg^-1

21.Steam burn is more severe than that of boiling water because

A. steam burn is independent of relative humidity
B. stem possesses greater heat energy per unit mass
C. water boils at a higher temperature
D. steam burn is dependent on relative humidity

Correct Answer: Option B

Explanation

The specific latent heat of vaporization of steam is 2.1 x 10⁶JKg^-1
while the energy required to raise the temperature of a unit mass of water from 0°c to 100°c = C x Dt = 4200 x 100 = 420000 = 4.2 x 10⁵ JKg^-1
∴ steam possesses greater heat energy per unit mass

I. change of state
II. Diffusion
III. Radiation
IV. Osmosis
which of the processes above can be explained using the kinetic theory?

A. I, II,III and IV
B. I, II and III
C. I, III and IV
D. I, II and IV

Correct Answer: Option D

23. Three similar cells each of e.m.f 2 v and internal resistance 2Ω are connected in parallel, the total e.m.f and total internal resistance are respectively

A. 6 v, 6.0Ω
B. 2 v, 0.7Ω
C. 2 v, 6.0Ω
D. 6 v, 0.7Ω

Correct Answer: Option B

Explanation

Total energy in parred connection is equal to emt of one cell, = 2v but total internal resistance is given by
(1)/r = (1)/r₁ + (1)/r₂ + (1)/r₃ = (1)/2 + (1)/2 + (1)/2 = (3)/2
∴ r = (2)/3 = 0.67Ω

24. When the human eye loses its power of accomodation, the defect is known as

A. short sightedness
B. presbyobia
C. astigmatism
D. long sightedness

Correct Answer: Option B

Explanation

presbyopia is loss of accommodation

25. When a red rose flower is observed in blue light, what colour does the observer see?

A. Red
B. Blue
C. Magenta
D. yellow
E. No correct option

Correct Answer: Option E

Explanation

The colour which an object presents to the eye is the colour of light it reflects. Red rose flower will therefore absorb any other colour and reflect red. Therefore when viewed in blue light, it has no colur to reflect and will therefore appear black. Although mixture of red light and blue light = magenta . NO correct option