JAMB Physics Past Questions & Answers - Page 254

1,267.

The length of a side of a metallic cube at 20°C is 5.0cm. Given that the linear expansivity of the metal is 4.0 x 10-5k-1, find the volume of the cube at 120°C .

A.

126.50cm3

B.

126.25cm3

C.

126.00cm3

D.

125.00cm3

Correct answer is A

Recall that: Volume = L * L * L → 5 * 5 * 5 = 125

Y = \(\frac{V_2 - V_1}{V_1 \times \theta}\)

3 x 4 x 10-5 = \(\frac{V_2 - 125}{125 \times (120 - 20)}\)

V2 = 126.50cm3

1,268.

The distance between the fixed points of a centigrade thermometer is 20cm. What is the temperature when the mercury level is 4.5cm above the lower mark?

A.

22.5oC

B.

29.0oC

C.

29.0oC

D.

100.0oC

Correct answer is A

20cm .... 100oC

4.5cm .... \(\theta\)

0cm ....0oC

\(\frac{4.5 - 0}{20 - 0}\) = \(\frac{0 - 0}{100 - 0}\)

\(\theta\) = 22.5oC

1,269.

A cube of side 10cm and mass 0.5kg floats in a liquid with only \(\frac{1}{5}\) of its height above the liquid surface. What is the relative density of the liquid?

A.

0.125cm-1

B.

0.250gcm-1

C.

0.625cm-1

D.

2.500cm-1

Correct answer is C

Height below liquid = 1 - \(\frac{1}{5}\) = \(\frac{4}{5}\)

volume of cube = 103cm3

volume of liquid displaced = \(\frac{4}{5}\) x 1000

= 800cm3

density of liquid displaced;

= \(\frac{500}{800}\)

= 0.625cm-1

1,270.

A load of 5N gives an extension of 0.56cm in a wire which obeys Hooke's law. What is the extension caused by a load of 20N?

A.

1.12cm

B.

2.14cm

C.

2.24cm

D.

2.52cm

Correct answer is C

\(\frac{F_1}{e_1}\) = \(\frac{F_2}{e_2}\)

\(\frac{5}{0.56}\) = \(\frac{20}{e_2}\)

e2 = 2.24cm