Physics Past Questions and Answers

A heating coil rated at 100W is used to boil off 0.5kg of boiling water. The time taken to boil off the water is [specific latent heat of vaporization of water = 2.3 x 10⁶Jkg^-1]

A 1.15 x 10⁹ s
B 1.15 x 10⁷ s
C 1.15 x 10⁵ s
D 1.15 x 10⁴ s

Question 22:

A mass of a liquid at 30^oC is mixed with a mass of the same liquid at 70^oC and the temperature of the mixture is 45^oC. Find the ratio of the mass of the cold liquid to the mass of the other liquid.

A 3 : 5
B 5 : 3
C 3 : 7
D 7 : 3

Question 23:

What happens when a gas expands at constant temperature?

A Its pressure decreases
B The total momentum of its molecules remains constant
C Its pressure decreases and the total momentum of its moleculees remains constant
D Its pressure decreses and the total kinetic energy of its molecule decreases

Question 24:

Ripples on water and light waves are similar because both

A Have the same frequency
B Can be refracted and diffracted
C Are longitudinal waves
D Have the same velocity

Question 25:

Under constant tension and constant mass per unit length, the note produced by a plucked string is 500Hz when the length of the string is 0.90m. At what length is the frequency 150Hz?

A 3m
B 4m
C 5m
D 6m