Waec Physics 1997 Past Questions and Answers

Question 16:

• WAEC 1997

Calculate the quantity of heat released when 100g of steam at 100°C condenses to water(Take the specific latent heat of vaporization of water as 2.3x \(10^6Jkg^{-1}\))

A. 2.3x\(10^{1}J\)
B. 2.3x\(10^{2}J\)
C. 2.3x\(10^{4}J\)
D. 2.3x\(10^{5}J\)
E. 3.3x\(10^{7}J\)

Question 17:

• WAEC 1997

A fixed mass of gas occupies a volume of 20\(cm^3\) at a fixed pressure of 700mmHg. Assuming that the temperature remains constant, what will be the volume of the gas at 750mmHg?

A. 2.5\(cm^3\)
B. 15.5\(cm^3\)
C. 18.7\(cm^3\)
D. 21.4\(cm^3\)
E. 72.5\(cm^3\)

Question 18:

• WAEC 1997

A converging lens of focal length 15cm is used to obtain a real image magnified \(1\frac{1}{2}\) times. Calculate the distance of the image from the lens?

A. 37.5cm
B. 22.5cm
C. 15cm
D. 7.5cm
E. 3.3cm

Question 19:

• WAEC 1997

A cup containing 100g of pure water at 20°C is placed in a refrigerator. If the refrigerator extracts heat at a rate of 840J per minute, calculate the time taken for the water to freeze. Neglect the heat capacity of the material of the cup. (Specific heat capacity of water =4.2J\(g^{-1}K^{-2}\))((Specific latent heat fusion of water =336J\(g^{-1}\)

A. 15minutes
B. 20 minutes
C. 42 minutes
D. 50 minutes
E. 84 minutes

Question 20:

• WAEC 1997

What is the frequency of a radio wave of wavelength 150m if the velocity of radio waves in free space is 3 x \(10^8ms^{-1}\)?

A. 4.5 x \(10^{10}\)Hz
B. 5x \(10^{9}Hz\)
C. 4.5 x \(10^{8}Hz\)
D. 2 x \(10^{7}Hz\)
E. 2 x \(10^{6}Hz\)