Waec Physics 1990 Past Questions and Answers

Question 61:

• WAEC 1990

What is the difference between a crystalline and an amorphous solid? A crystalline solid

A. Has cubic structure while amorphous solid has hexagonal structure
B. Has regularly-repeating pattern while an amorphous solid has not
C. Is white while amorphous solid is yellow
D. Is always hard while amorphous solid is always soft
E. Melts on heating while an amorphous solid sublimates on heating.

Question 62:

• WAEC 1990

Which of the following is not an evidence of the particle nature of matter?

A. Diffusion
B. Brownian motion
C. Diffraction
D. Crystal structure
E. Photoelectricity

Question 63:

• WAEC 1990

(a) Using a suitable diagram, explain how the following can be obtained from a velocity-time graph (i) acceleration; (ii) retardation; (iii) total distance covered.
(b) Show that the displacement of a body moving with uniform acceleration a is given by \(s = ut + \frac{1}{2} at^{2}\) where u is the velocity of the body at time t = 0.
(c) A particle moving in a straight line with uniform deceleration has a velocity of 40ms\(^{-1}\) at a point P, 20ms\(^{-1}\) at a point Q and comes to rest at a point R where QR = 50m. Calculate the: (i) distance PQ; (ii) time taken to cover PQ; (iii) time taken to cover PR.

Question 64:

• WAEC 1990

(a) Define the boiling point of a liquid.
(b) Describe an experiment to determine the boiling point of small quantity of a liquid.
(c) A piece of copper of mass 300 g at a temperature of 950°C is quickly transferred to a vessel of negligible thermal capacity containing 250 g of water at 25°C. If the final steady temperature of the mixture is 100°C, calculate the mass of the water that will boil away.
[Specific heat capacity of copper = \(4.0 \times 10^{2} Jkg^{-1} K^{-1}\); Specific heat capacity of water = \(4.2 \times 10^{3} Jkg^{-1} K^{-1}\); Specific latent heat of vaporization of steam = \(2.26 \times 10^{6} Jkg^{-1}\)
(d) State four other effects of heat on a substance other than expansion.

Question 65:

• WAEC 1990

(a) Define the capacitance of a capacitor.
(b) State three factors on which the capacitance of a parallel plate capacitor depends.
(c) Derive a formula for the energy W stored in a charged capacitor of capacitance C carrying a charge Q on either plate.
(d) Two capacitors of capacitance 4\(\mu F\) and 6\(\mu F\) are connected in series to a 100V d.c supply. Draw the circuit diagram and calculate the (i) charge on either plate of each capacitor (ii) p.d. across each capacitor; (iii) energy of the combined capacitors.