Waec Physics Past Questions For Year 1990
Question 16
The body P shown in the diagram above is in equilibrium. If the mass Q of the body is 10kg, calculate the tension T in the string. (Take g = 10ms2)
- A. 20/√3N
- B. 20N
- C. 50N
- D. 200√3N
- E. 200N
Question 17
Which of the following is not a suitable method for reducing loss of heat from a piece of hot iron?
- A. Wrapping it in cotton wool
- B. painting it black
- C. Placing it in a vacuum
- D. Placing it on rubber supports
- E. Keeping it in a closed wooden box
Question 18
Heat transfer by convection in a liquid is due to the
- A. translatory motion of the molecules of the liquid
- B. increased vibration of the molecules of the liquid about their mean positions
- C. expansion of the liquid as it is heated
- D. latent heat of vaporization of the liquid
- E. ability of the liquid to evaporate at all temperatures
Question 19
How much heat is given out when a piece of iron of mass 50g and specific heat capacity 460 Jkg-1k-1 cools from 85oC to 25oC?
- A. 1.38 x 106 J
- B. 2.53x104J
- C. 7.66x103J
- D. 1.38x103J
- E. 1.27 X103J
Question 20
lf the temperature of a small quantity of water in a closed container is gradually increased from 0o to 40oC then the density of the water within this range
- A. increases for a while and then decreases
- B. decreases for a while and then increases
- C. increases gradually
- D. decreases gradually
- E. remains the same
