WAEC Physics Past Questions & Answers - Page 233

1,161.

The pressure of air in a tire is \(22.5Nm^{-2}\) at 27°C. If the air in the tyre heats up to 47°C, calculate the new pressure of the air, assuming that no air leaks out and that the change in volume of the air can be neglected.

A.

\(21.10Nm^{-2}\)

B.

\(24Nm^{-2}\)

C.

\(39.07Nm^{-2}\)

D.

\(45Nm^{-2}\)

E.

\(97.25Nm^{-2}\)

Correct answer is B

\(\frac{P_1}{T_1}=\frac{P_2}{T_2};P_2= \frac{22.5\times320K}{300K}=24Nm^{-2}\)

1,162.

\(500cm^{-3}\) of a gas is collected at 0°C and at a pressure of 72cm of mercury. What is the volume of the the gas at the same temperature and at a pressure of 76cm of the same mercury?

A.

\(\frac{76\times500}{72}cm^3\)

B.

\(\frac{72\times500}{76}cm^3\)

C.

\(\frac{72\times76}{500}cm^3\)

D.

\(\frac{76}{72\times500}cm^3\)

E.

\(\frac{72}{76\times500}cm^3\)

Correct answer is B

\(P_1V_1=P_2V_2, V_2= \frac{72\times500}{76}cm^3\)

1,163.

An electric kettle rated 1500W boils away 0.3kg of a liquid at its boiling point every 300s. Calculate the specific latent heat of the vaporisation of the liquid

A.

1.5 x \(10^6Jkg^-1\)

B.

1.35 x \(10^6Jkg^-1\)

C.

1.5 x \(10^5Jkg^-1\)

D.

4.5 x \(10^2Jkg^-1\)

E.

3 x \(10^2Jkg^-1\)

Correct answer is A

Pt=mI; I=\(\frac{1500\times300}{0.3}=1.5\times10^6Jkg^-1\)

1,165.

A metal rod of length 40cm at 20°C is heated to a temperature of 45°C. If the new length of the rod is 40.05cm. Calculate its linear expansitivity

A.

1.2 x \(10^{-5}K{-1}\)

B.

2.5x \(10^{-5}K{-1}\)

C.

3.5x \(10^{-5}K{-1}\)

D.

4.5x \(10^{-5}K{-1}\)

E.

5x \(10^{-5}K{-1}\)

Correct answer is E

\(\alpha = \frac{I_2-I_1}{I_1(\theta_2-\theta_1)} \\ \Rightarrow \frac{40.05 - 40}{40 \times (45-20)} = 5.0 \times10^{-5}\)