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JAMB Physics Past Questions & Answers - Page 44

217.

A rectangular solid block has length 10cm, breadth 5cm and height 2cm. If it lies on a horizontal surface, and has density 100kg/m3, calculate the pressure it exerts on the surface.

A.

20 N/m2

B.

100 N/m2

C.

400 N/m2

D.

300 N/m2

Correct answer is A

P = F
A
= mg
A
= (ρ × v) × g
A
= ρ × (A × h) × g
A


P = 100 × 2 × 102 × 10 = 20 N/m2

218.

Which of the following statements are correct of the production and propagation of waves?
I. vibration produces waves
II. waves transmit energy along the medium
III. the medium through which the wave travels does not travel with the wave
IV. waves do not require any medium for transmission

A.

I & IV only

B.

II & IV only

C.

III & IV only

D.

I, II and III only

Correct answer is D

- Waves are produced by vibration
- Waves transmit energy along the medium
- Particles of a medium vibrate with the wave motion without the entire medium
- Some waves require medium for transmission (mechanical).

219.

The mass of water vapour in a given volume of air is 0.05g at 20°C, while the mass of water vapour required to saturate it at the same temperature is 0.15g. Calculate the relative humidity of the air.

A.

3.33%

B.

5.55%

C.

33.33%

D.

55.55%

Correct answer is C

RH = mass of water vapour in volume of air
mass of water vapour for saturation

 

RH = m
M
= 0.05
0.15
× 100 = 5
0.15
= 500
15
= 33.33%

220.

A safety precaution designed to prolong the life of a lead acid accumulator is

A.

By topping up the cells with concentrated acid

B.

The use of naked flame when charging the battery

C.

Keeping the specific gravity of the electrolyte within specified range

D.

By connecting wires to the terminals directly when testing the level of charging

Correct answer is C

- Topping is done with distilled water
- Naked flame should be avoided when charging the battery
- Direct connection of wires to the terminals should be avoided.