Physics 2013 JAMB Past Questions

1. When a brick is taken from the earth's surface to the moon, its mass

A. remains constant
B. reduces
C. increases
D. becomes zero

Correct Answer: Option A

2.The resultant of two forces is 50N. If the forces are perpendicular to each other and one of them makes an angle 0f 30^o with the resultant, find its magnitude.

A. 100.0N
B. 57.7N
C. 43.3N
D. 25.0N

Correct Answer: Option C

Explanation

F = 50Cos30^o = 43.3

3. The pair of physical quantities that are scalar only are ?

A. volume and area
B. moment and momentum
C. length and displacement
D. Impulse and time

Correct Answer: Option A

Explanation

This is because volume and the area have only magnitude but no direction

4. A simple pendulum of length 0.4m has a period of 2s. What is the period a similar pendulum of length 0.8m at the same place?

A. 8s
B. 4s
C. 2 $\sqrt{2} s$

\sqrt{2} s

Correct Answer: Option C

Explanation

T₂ =

\sqrt{\frac{L^{2} \times T_{1}^{2}}{L_{1}}}

\sqrt{\frac{0.8 \times 2^{2}}{0.4}}

= 2

\sqrt{2} s

5. A train with an initial velocity of 20ms^-1 is subjected to a uniform deceleration of 2m^-2. The time required to bring the train to a complete halt is?

A. 5s
B. 10s
C. 20s
D. 40s

Correct Answer: Option B

Explanation

t =

\frac{v - u}{a}

\frac{0 - 20}{- 2}

= 10s

6. Calculate the apparent weight loss of a man weighing 70kg in an elevator moving downwards with an acceleration of 1.5ms^-2.

[g = 10ms^-2]

A. 686N
B. 595N
C. 581N
D. 105N

Correct Answer: Option D

Explanation

Wt loss = mg - m (g - a)

= 70 x 10 - 70 (10 - 1.5) = 105N

7. 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

Correct Answer: Option C

Explanation

\frac{0.25 \times 10^{3}}{1.25 \times 10^{3}}

= 0.2

8. An object is moving with a velocity of 5m^-1. At what height must a similar body be situated to have a potential energy equal in value with kinetic energy of the moving body?

A. 25.0m
B. 20.0m
C. 1.3m
D. 1.0m

Correct Answer: Option C

Explanation

P.E = K.E

Therefore, h =

\frac{v^{2}}{2 g} = \frac{5^{2}}{2 \times 10}

= 1.25

Approx 1.3 (C)

9. If a pump is capable of lifting 5000kg of water through a vertical height of 60m in 15 min, the power of the pump is

A. 2.2.5 x 10 ⁵js^-1
B. 2.5 x 10⁴js^-1
C. 3.3 x 10³js^-1
D. 3.3 x 10²js^-1

Correct Answer: Option C

Explanation

P =

\frac{m g h}{t}

P =

\frac{5000 \times 10 \times 60}{(15 \times 60) s}

P = 3333.3333

P = 3.3 x 10³js^-1

10. The coefficient of friction between two perfectly smooth surface is

A. infinity
B. one
C. half
D. zero

Correct Answer: Option D

11. What effort will a machine of efficiency 90% apply to lift a load of 180N if its efforts arm is twice as long as its load arm?

A. 80N
B. 90N
C. 100N
D. 120N

Correct Answer: Option C

Explanation

M.A. = $\frac{E f f \times V . R .}{100}$

M.A. = $\frac{90 \times 2}{100}$

M.A. = 1.8

E = $\frac{L}{M . A .}$

E = $\frac{180}{1.8}$

E = 100N

12. Calculate the work done when a force of 20N stretches a spring by 50mm.

A. 0.5J
B. 1.5J
C. 2.0J
D. 2.5J

Correct Answer: Option A

Explanation

W =

\frac{1}{2} F e

W =

\frac{1}{2} \times 20 \times 0.05

W = 0.5J

13. At what depth below the sea-level would one experience a change of pressure equal to one atmosphere? Density of sea water = 1013kg^-3, one atmosphere = 0.01 x 10⁵Nm^-2, g = 10ms^-2

A. 0.1m
B. 1.0m
C. 10.0m
D. 100.0m

Correct Answer: Option C

Explanation

H =

\frac{P}{e_{g}}

H =

\frac{1.01 \times 10^{5}}{1013 \times 10}

H = 9.97

14. What volume of alcohol will have same mass as 4.2m^-3 of petrol?

Density of alcohol = 8.4 x 10²kgm^-3, density of petrol =7.2x10³kgm^-3

A. 0.8m³
B. 1.4m³
C. 3.6m³
D. 49.m³

Correct Answer: Option C

Explanation

M_p = e_p x V_p

M_p = 7.2 x 10² x 4.2 = 3024

V_A =

\frac{M}{e_{A}}

V_A =

\frac{3024}{8.4 \times 10^{2}}

V_A = 3.6

15. Calculate the length which corresponds to a temperature of 20^oC if the ice and steam points of an unguarded thermometer are 400 mm apart

A. 20mm
B. 30mm
C. 60mm
D. 80mm

Correct Answer: Option D

Explanation

At 100^oC = 400

Therefore,

At 20^oC =

\frac{400}{100} \times \frac{20}{1}

= 80

16. A wire of length 100.0m at 30^o has linear expansive of 2x10^-5K^-1 Calculate the length of the wire at a temperature of - 10^oC

A. 100.08m
B. 100.04m
C. 99.96m
D. 99.92m

Correct Answer: Option D

Explanation

L_{2} = L_{1} + α (θ_{2} - θ_{1})

= 100 + 0.00002(-10-30) = 99.92

17. A gas at a pressure of 10⁵Nm^-2expands from 0.6m^-3 to 1.2m³ at constant temperature, the work done is

A. 7.0 x 10⁶J
B. 6.0 x 10 ⁶J
C. 6.0 x 10 ⁵J
D. 6.0 x 10 ⁴J

Correct Answer: Option D

Explanation

W =

\frac{W_{1} \times V_{1}}{V_{2}}

W =

\frac{10 \times 0.6}{1.2}

W = 6.0 x 10 ⁴J

18. Two liquids X and Y having the same mass are supplied with the same quantity of heat. If the temperature rise in X is twice that of Y, the ratio of specific heat capacity of X to that of Y is

A. 2:1
B. 1:2
C. 4:1
D. 1:4

Correct Answer: Option B

Explanation

x_{θ}

= MC

y_{θ}

x_{θ}

= 2

\times y_{θ}

MC(2

y_{θ}

) = MC

y_{θ}

⇒ 2C = C

=1 : 2

19. Food cook quicker in salt water than in pure water because of the effect of

A. dissolved substances on the boiling point
B. atmospheric pressure on the boiling point
C. food nutrients on the thermal energy
D. salts on the thermal conductivity of water

Correct Answer: Option A

Explanation

Water impurities (such as salt water) boils at higher temperature than pure water. This helps to cook the food quicker.

20. Steam from boiling water causes more damage on the skin than does boiling water because

A. water has a high specific heat
B. steam has latent heat of fusion
C. the steam is at a highter temperature than the water
D. steam brings heat more easily by convection

Correct Answer: Option C

21. What will happen to the boiling point of pure water when it is heated in a place 30m below sea level?

A. It will be more than 100 ^oC
B. It will be last than 100 ^oC
C. It will still be at 100 ^oC
D. It will be fluctuating

Correct Answer: Option A

22. The rise or fall of a liquid in a narrow tube is because of the

A. viscosity of the liquid
B. surface tension of the liquid
C. friction between the walls of the tube and the liquid
D. osmotic pressure of the liquid

Correct Answer: Option C

23. The mechanism of heat transfer from one point to another through the vibration of the molecules of the medium is

A. covection
B. conduction
C. radiation
D. diffusion

Correct Answer: Option B

24. A wave that travels through stretched strings is known as

A. electromagnetic wave
B. micro wave
C. mechanical wave
D. seismic wave

Correct Answer: Option C

25. A transverse wave and a longitudinal wave travelling in the same direction in a medium differ essentially in their

A. frequency
B. amplitude
C. direction of vibration of the particles of the medium
D. period of vibration of the particles of the medium