O-LevelPhysicsForces5054/21 · Oct/Nov 2016 · Q17 Marks
A car of mass 800 kg is travelling at a speed of 25 m/s along a straight, horizontal road.
- (a)State how velocity differs from speed.[1]
- (b)The driver presses the accelerator and the speed of the car starts to increase from 25 m/s. The car accelerates at 1.5 m/s².
- (b)(i)Calculate the resultant force acting on the car as it accelerates.[2]
- (b)(ii)Explain why the forward force acting on the car due to the engine is greater than the value in (b)(i).[2]
- (b)(iii)Determine the speed of the car 4.0 s after it starts to accelerate.[2]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2016). The mark or mark type is shown in brackets.
- [B1] velocity/it has a direction/is a vector
- [C1] (F = )ma or 800 × 1.5
- [A1] 1200 N
- [B1] friction/air resistance acts on car
- [B1] opposes force due to engine
- [C1] (Δv = )at or 1.5 × 4.0 or 6.0
- [A1] 31 m/s
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