A car starts from rest and moves in a straight line with constant acceleration for a distance of 200m, reaching a speed of 25 ms¯¹. The car then travels at this speed for 400 m, before decelerating uniformly to rest over a period of 5 s.
- (a)Find the time for which the car is accelerating.[2]
- (b)Sketch the velocity-time graph for the motion of the car, showing the key points.[2]
- (c)Find the average speed of the car during its motion.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.
- [M1] For use of s = (u+v)/2 * t or other complete method to find t
- [A1] t = 16s
- [B1] Through (0, 0) and positive t-axis
- [B1] FT their value of t from part (a) (t +16 + 5)
- [M1] Total distance = 200+400+1/2*25*5 [= 662.5] (Or trapezium 1/2*25(16+37)[= 662.5]) (Or 200+400+(25+0)/2 * 5)
- [A1] Average speed = 662.5/37 = 17.9 ms¯¹ (3 s.f.) (Allow 1325/74 = 17 67/74)
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