WAEC Physics Past Questions & Answers - Page 123

611.

A rod of initial length 2m at a temperature of 25oC is heated to 80oC. Calculate the increase in length of the rod if its linear expansivity is 4.0 x 10-3K-1

A.

0.26m

B.

0.44m

C.

0.53m

D.

0.84m

Correct answer is B

\(l_2 - l_1 = \alpha l_1 (\theta_2 - \theta_1) = 4.0 \times 10^{-3} \times 2(80 - 25)\)

= 0.44m

612.

A faulty thermometer registers 102.5oC t 100oC. If the thermometer has no zero hour, what will it register at 55oC?

A.

54.6oC

B.

55.0oC

C.

56.0oC

D.

56.4oC

Correct answer is D

x = \(\frac{102.5 \times 55}{100}\)

= 56.375oC

613.

A machine of efficiency 80% is used to lift a box. If the effort applied by the machine is twice the weight of the box. Calculate the velocity ratio of the machine

A.

0.50

B.

0.63

C.

0.80

D.

1.60

Correct answer is B

Y = \(\frac{M.A}{V.R} \times \frac{100}{1}\)

= \(\frac{\frac{1}{2}}{V.R} \times \frac{100}{1}\)

V.R = 0.625

614.

A stone of mass 0.5kg is dropped from a height of 12m. Calculate its maximum kinetic energy. [g = 10ms-1]

A.

3.0J

B.

6.0J

C.

30.0J

D.

60.0J

Correct answer is D

K.E = P.E = mgh

= 0.5 x 10 x 12 = 60J

615.

Electric energy is measured in

A.

ampere

B.

coulomb

C.

kilowatt-hour

D.

kilowatt

Correct answer is C

No explanation has been provided for this answer.