Question

8.(c) A car starts from rest and accelerates uniformly for 20s to attain a speed of 25ms⁻¹. It maintains this speed for 30s before decelerating uniformly to rest. The total time for the journey is 60s.
(i) Sketch a velocity–time graph for the motion.
(ii) Use the graph to determine: (iii) Total distance travelled (iv) Deceleration of the car.

Accepted Answer

(i) The graph is a trapezium: velocity rises linearly from 0 to 25ms⁻¹ over 0–20s, stays constant at 25ms⁻¹ from 20–50s, then falls linearly to 0 from 50–60s.
(iii) Total distance = area under the graph = ½(60+30)×25 = ½×90×25 = 1125m.
(iv) Deceleration = (0−25)/(60−50) = −2.5ms⁻² (i.e. a deceleration of 2.5ms⁻²).

WAEC Physics 2018 Theory — Question 13

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