WAEC Physics Past Questions & Answers - Page 258

1,286.

The pressure of a fixed mass of gas is 2.0 x 105Nm-2 at a known temperature. Assuming that the temperature remains constant, what will be the pressure of the gas if its volume is halved?

A.

1.0x105Nm-2

B.

2.0X105Nm-2

C.

3.0x105Nm-2

D.

4.0 x105Nm-2

E.

5.0 x105Nm-2

Correct answer is D

No explanation has been provided for this answer.

1,288.

A platinum-resistance thermometer has a resistance of 5Ω at 0°C and 9Ω at l00°C. Assuming that resistance changes uniformly with temperature, calculate the resistance of the thermometer when the temperature is 45°C.

A.

13.9 Ω

B.

8.9 Ω

C.

6.8 Ω

D.

3.2 Ω

E.

1.8 Ω

Correct answer is C

\(\frac{\theta}{100} = \frac{R_ {\theta} - R_0}{R_{100} - R_0}\)

\(\frac{45}{100} = \frac{R_{\theta} - 5}{9 - 5}\)

\(45 \times 4 = 100(R_{\theta} - 5)\)

\(180 = 100R_{\theta} - 500\)

\(180 + 500 = 100R_{\theta}\)

\(R_{\theta} = \frac{680}{100}\)

\(R_{\theta} = 6.8 \Omega\)

1,289.

Two simple pendula x and y make 400 and 500 oscillations respectively in equal time. If the period of oscillation of x is 1.5 seconds, what is the period of oscillation of y?

A.

0.53s

B.

0.83s

C.

1.20s

D.

1.50s

E.

1.88s

Correct answer is C

where f = \(\frac{oscillations}{time}\)

period = 1/ f or \(\frac{time}{oscillations}\)

For pendulum x:

where period = 1.5 and oscillation = 400

time = oscillations X 1.5 = 600s

For pendulum y:

\(\frac{time}{oscillations}\) → 600/500

period for y = 1.2s

period =   

 

1,290.