JAMB Physics Past Questions & Answers - Page 323

1,611.

The length of mercury thread when it is at 0°C, 100°C and at an unknown temperature \(\theta\) is 25mm, 225mm and 175mm respectively. The value of \(\theta\) is

A.

85.0oC

B.

80.0oC

C.

75.0oC

D.

70.0oC

Correct answer is C

\(\frac{175 - 25}{225 - 25} = \frac{x - 0}{100 - 0}\)

\(\frac{150}{200} = \frac{x}{100}\)

\(x = \frac{150 \times 100}{200}\)

= 75°C

1,612.

An empty 60 litre petrol tank has a mass of 10kg. Its mass when full of fuel of relative density 0.72 is

A.

7.2kg

B.

33.2kg

C.

43.2kg

D.

53.2kg

Correct answer is C

R.d = \(\frac{\text {density of petrol}}{\text{density of water}}\)

0.72 = \(\frac{\text{density of petrol}}{1000}\)

Density of petrol =720kgm3

mass of petrol = 720 x 60 x 10-3

=43.2kg

1,613.

A liquid of mass 1.0 x 103kg fills a rectangular tank of length 2.5m and width 2.0m. If the tank is 4m high, what is the pressure at the middle of the tank?[g = 10ms-2]

A.

1.0 x 104Nm-2

B.

2.0 x 103Nm-2

C.

1.5 x 103Nm-2

D.

1.0 x 103Nm-2

Correct answer is D

Density of liquid = \(\frac{1 {\times} 10^3}{2.5 {\times} 2 {\times} 4}\)

= 50kgm3

pressure heg = 50 x 10 x \(\frac{4}{2}\)

= 1 x 103Nm-2

1,614.

A piece of wire gauze can be made to lie on water because

A.

the wire guaze is less dense than water

B.

the water molecules repels the wire guaze upwards

C.

the water surface has the effect of an elastic thin skin

D.

of the cohensive forces between the water and the wire guaze molecules

Correct answer is C

No explanation has been provided for this answer.

1,615.

A cube of sides 0.1m hangs freely from a string. What is the upthrust on the cube when totally immersed in water? [density of water is 1000kgm-2, g = 10ms-2]

A.

1000 N

B.

700 N

C.

110 N

D.

10 N

Correct answer is D

Volume of water displaced = volume of cube

therefore, 0.1 x 0.1 x 0.1 = 0.001m3

mass of H2O = 0.001 X 1000

= 1kg

upthrust = mg

= 1 x 10

=10N