WAEC Physics Past Questions & Answers - Page 218

1,088.

Air at temperature 527oC and pressure 30 atmospheres is admitted into the cylinder of an engine. Calculate the pressure of the gas when it has expanded to 5 times its volume and cooled to 127oC as it leaves the engine

A.

1.5 atmospheres

B.

2.5 atmospheres

C.

3.0 atmospheres

D.

12.8 atmospheres

E.

15.0 atmospheres

Correct answer is C

\(\frac{V_1P_1}{T_1} = \frac{V_2P_2}{T_2}\)

\(\frac{1 \times 30}{527 + 2733} = \frac{5P_2}{127 + 273}\)

\(\frac{30}{800} = \frac{5p_2}{400}\)

P2 = \(\frac{400 \times 30}{800 \times 5}\)

= 3

1,089.

If the cubic expansivity of brass between 27oC and 100oC is 5.7 x 10-5K-1, What is its linear expansivity?

A.

2.85 x 10-5K-1

B.

1.90 x 10-5K-1

C.

1.86 x 10-5K-1

D.

1.70 x 10-5K-1

E.

1.63 x 10-5K-1

Correct answer is B

\(\alpha\) = \(\frac{\Delta}{3} = \frac{5.7 \times 10^{-5}}{3}\)

= 1.90 x 10-5K-1

1,090.

The average kinetic energy of the molecules of a perfect gas is directly proportional to the

A.

pressure exerted by the gas

B.

volume of the gas molecule

C.

kelvin temperature of the gas

D.

volume of the gas container

E.

celcius temperature of the gas

Correct answer is C

The average kinetic energy of the molecules of a perfect gas is directly proportional to the Absolute temperature that is the temperature measured using the kelvin scale.