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 :
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 drawnThey move together at 0.7 m s-1 in the initial direction of B