Question 11
(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.
Observation
Part (a)(i): Candidates performance was fair. Many candidates did well while some candidates got
the wrong definition and the unit in word. Conventionally, the unit of force when spelt in word
should be in lower case.
(ii) Majority of the candidates were able to list types of solid friction correctly. Performance
was good
Part (b)(i): Candidates performance was fair. Many candidates had difficulty with the sketch.
(ii): The calculation was sequel to the sketch. Many candidates who could not sketch correctly
lost marks.
The expected answer is
(a) (i) Definition of force
Action/push/pull that changes/tends to change the state of rest or of uniform motion in straight
line.
Its unit is newton (N)
(ii) Types of solid friction
- dynamic (friction)
- static (friction)
(b) (i) Velocity-time graph for journey
