Physics Paper 2 WASSCE (PC), 2019

 

Question 8

(a) (i) Define pressure.
(ii) State two factors that determine the pressure at a point in a liquid.
(iii) The water in a well is 15 m deep. Calculate the total pressure at the base on a day when the atmospheric pressure is 75.5 cm Hg

 

(b) State two differences between mass and weight of a body.

 

(c) Two bodies A and B with masses 0.2 kg and 0.5 kg respectively, are places in a narrow path as illustrated in the diagram below (i) State two conditions under which A and B would collide when both are in motion.

(ii) Given that A and B, travelling initially at 5.0 ms-1 and 3.0 ms-1respectively, undergo a head-on collision such that there is a change in the total mechanical energy, calculate the velocity with which they move after collision.

(iii) What conclusions can be drawn from the result in 8 (c)(ii)?

Observation

Part (a) Candidates performance was below average
Part (b) Performance was fair
Part (c) Performance was low.
The expected answer is :

8(a)(i) Definition of pressure
Force acting normally per unit area

(ii)Factors that determine the pressure at a point in a liquid
- Depth
- Density of the liquid
- Acceleration due to gravity

(iii)Calculation of total pressure
P = hpg + H

 

(b)Differences between mass and weight of a body

Mass

Weight

Amount of matter in a body

Force of gravity on a body

Scalar quantity

Vector quantity;

SI unit is kilogram (kg)

SI unit is newton (N)

Constant everywhere

Varies from place to place

Measured with a beam balance

Measured with a spring balance

 

(c) (i)Conditions under which A and B will collide

- They must move towards each other
- If they move in the same direction, the one behind must move with higher
velocity/speed

(ii)Calculation of velocity with which A and B move after collision

(iii)Conclusion that could be drawn
They move together at 0.7 m s-1 in the initial direction of B