PHYSICS · Subjective · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A car starts from rest at point O, moves along a straight road, and comes to rest again at point P after 40s. Its motion consists of three successive stages:
Stage I: Uniform acceleration for 10s until it reaches a speed of 20ms−1.
Stage II: Constant speed for the next 15s.
Stage III: Uniform retardation bringing it to rest in the remaining time.
(a) Draw a labelled velocity–time graph for the complete journey.
(b) From the graph determine (i) the magnitude of the acceleration in Stage I, and (ii) the magnitude of the retardation in Stage III.
(c) Calculate the total displacement OP.
(d) On the basis of your velocity–time graph, draw a qualitative position–time graph for the journey, indicating clearly the nature of the curve in each stage. Justify the shape chosen for each segment with reference to slope and curvature.