# 2021 - JAMB Physics Past Questions & Answers - page 1

1

The slope of the straight line displacement-time graph indicates?

A

distance traveled

B

uniform velocity

C

uniform acceleration

D

uniform speed

CORRECT OPTION: b

Uniform velocity = $$\frac{\bigtriangleup s}{\bigtriangleup t}$$

2

A man will exert the greatest pressure when he?

A

lies flat on his back

B

lies on his belly

C

stands on both feet

D

stands on the toes of one foot

CORRECT OPTION: d

Pressure is inversely proportional to A, hence P $$\propto$$ $$\frac{1}{A}$$

3

Which of the following physical quantities units are derived?

I. Area
II. Thrust
III. Pressure
IV. Mass

A

I, II, III and IV

B

I, II, and III only

C

I, II, and IV only

D

I and IV only

CORRECT OPTION: b
4

A ball of mass 0.5kg moving at 10ms$$^{-1}$$ collides with another ball of equal mass at rest. If the two balls move off together after the impact, calculate their common velocity.

A

0.2ms$$^{-1}$$

B

0.5ms$$^{-1}$$

C

5.0ms$$^{-1}$$

D

5.5ms$$^{-1}$$

CORRECT OPTION: c

m$$_{1}$$ u$$_{1}$$ + m$$_{2}$$ u$$_{2}$$ = (m$$_{1}$$ + m$$_{2}$$)v

m$$_{1}$$ = 0.5kg, u$$_{1}$$ = 10ms$$^{1}$$, m$$_{2}$$ = 0.5kg, u$$_{1}$$ = 0

$$\therefore$$ (0.5kg x 10) + (0.5 x 0) = (0.5 + 0.5)v

v = 5ms$$^{1}$$

5

The motion of a body is simple harmonic if the?

A

acceleration is always directed towards a fixed point

B

path of motion is a straight line

C

acceleration is proportional to the square of the distance from a fixed point

D

acceleration is constant and directed towards a fixed point

CORRECT OPTION: a

In mechanics and physics, simple harmonic motion is a special type of periodic motion where the restoring force on the moving object is directly proportional to the magnitude of the object's displacement and acts towards the object's equilibrium position. Wikipedia

6

Which of the following is not correct about the molecules of a substance in a gaseous state? They

A

are in a constant state of motion

B

have different speeds

C

have a temperature which is measured by the average kinetic energy

D

The collision between the gases is perfectly inelastic

CORRECT OPTION: d

All collisions between gas molecules are perfectly elastic; all kinetic energy is conserved. When cars collide, energy is lost to bending bumpers and metal. Molecules do not act like this. Instead, they act like billiard balls. More

7

A given mass of gas has a pressure of 80 Nm$$^{-2}$$ at a temperature of 47 C. If the temperature is reduced to 27 C with volume remaining constant, the new pressure is?

A

46.0 Nm$$^{-2}$$

B

75.0 Nm$$^{-2}$$

C

80.0 Nm$$^{-2}$$

D

85.3 Nm$$^{-2}$$

CORRECT OPTION: b

$$\frac{P_{1}}{T_{1}} = \frac{P_{2}}{T_{2}}$$

P$$_{1}$$ = 80Nm$$^{2}$$
T$$_{1}$$ = 47 + 273 = 320k
T$$_{2}$$ = 27 + 273 = 300k
P$$_{2}$$?

$$\therefore$$ = P$$_{2}$$ = $$\frac{P_{1}T_{2}}{T_{1}}$$

= $$\frac{80 \times 300}{320}$$

= 75.Nm$$^{2}$$

8

0.5kg of water at 10ºC is completely converted to ice at 0ºC by extracting (88000) of heat from it. If the specific heat capacity of water is 4200jkg$$^{1}$$ Cº. Calculate the specific latent heat of fusion of ice.

A

9.0kjkg$$^{-1}$$

B

84.0kjkg$$^{-1}$$

C

134.0kjkg$$^{-1}$$

D

168.0kjkg$$^{-1}$$

CORRECT OPTION: c

Given

Heat(H) = 88,000J,

Mass(M)= 0.5kg,

Specific heat capacity of water(C) = 4200JkgºC,

Specific latent heat of fusion(L) = ?,

Temperature change(Δθ) =  θ2 -  θ1 =  (10 - 0)° = 10°

H = MCΔθ + ML

H = M(CΔθ + L) => $$\frac{H}{M}$$ = CΔθ + L

L = $$\frac{H}{M}$$ -  CΔθ = $$\frac{88,000}{0.5}$$ - 4200 $$\times$$ 10

L = 176,000 - 42000 = 134,000

L = 134,000 or 134kj/kg

9

Which of the following instruments may be used to measure relative humidity?

A

Hydrometer

B

Manometer

C

Hygrometer

D

Hypsometer

CORRECT OPTION: c

A hygrometer is an instrument used to measure the amount of water vapour in the air, soil, or confined spaces. Relative humidity (RH) is a measure of the amount of water vapor in a water-air mixture compared to the maximum amount possible.

10

A source of sound produces waves in air of wavelength 1.65m. If the speed of sound in air is 330ms$$^{-1}$$, the period of vibration in air is?

A

200

B

0.005

C

0.5

D

0.02

CORRECT OPTION: b

v = $$\frac{\lambda}{T}$$

v = 330ms$$^{-1}$$

$$\lambda$$ = 1.65m

330 = 1.65

T = $$\frac{1.65}{330}$$ = 0.005s

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