Question 4216:

• WAEC 2019

(a) State the principle of operation of fibre optics.
(b) State two applications of fibre optics in medicine.

Question 4217:

• WAEC 2019

(a) Define diffusion
(b) State two factors that affect the rate of diffusion

Question 4218:

• WAEC 2019

(a) (i) State Newton’s Law of Universal Gravitation.
(ii) Define gravitational field.
(b) (i) Derive the equation relating the universal gravitational constant, G, and the acceleration of free fall, g, at the surface of the earth from Newton’s law of universal gravitation.
(ii) State two assumptions for which the relationship in 8(b)(i) holds.

(c) Calculate the force of attraction between a star of mass 2.00 x 1030 kg and the earth assuming the star is located 1.50 x 108 km from the earth. [Mass of the earth = 5.98 x 1024kg; G = 6.67 x 10-11N m\(^{2}\) kg-2; g = 10 m s\(^{-2}\)

(d) (i) Define escape velocity.
(ii) State two differences between the acceleration of free fall (g) and the universal gravitational constant (G).

Question 4219:

• WAEC 2019

(a) (i) Explain latent heat.
(ii) State two factors that affect the rate of evaporation of a liquid

(b) Explain each of the following observations:
(i) On a dry day, water in a clay pot is cooler than water in a closed plastic container;
(ii) Food gets cooked faster in a pressure cooker than in an ordinary cooking pot.

(c) State two effects of heat on a substance.

(d) A 40 V electric heater is used to supply a current of 12 A for 1400 s to a body of mass 1.5 kg at the melting point of the body. The body melts and its temperature rises through 60\(^o\)C in an extra 72 s. Determine the:
(i) latent heat of fusion of the body;
(ii)specific heat capacity of the body.

Question 4220:

• WAEC 2019

(a) (i) Define force and state its S.I unit.
(ii) List the two types of solid friction.
(b) A car travelling at a constant speed of 30 ms-1 for 20 s was suddenly decelerated when the driver sighted a pot-hole. It took the driver 6 s to get to the pot-hole with a reduced speed of 18 ms-1. He maintained the steady speed for another 10 s to cross the pot-hole. The brakes were then applied and the car came to rest 5 s later.
(i) Draw the velocity-time graph for the journey.
(ii) Calculate the deceleration during the last 5 s of the journey.
(iii) Calculate the total distance covered.