Fig 2.26 shows the displacement-time graph for the motion of two boys A and B along a straight road in the same direction. Answer the following:
(i) When did B start after A ?
(ii) How far away was A from B when B started?
(iii) Which of the two has greater velocity ?
(iv) When and where did B overtake A ?

Explanation

(i) B started his motion 2 h later from the start of A.
(ii) When B started, A was at distance 10 km away from B.
(iii) B has greater velocity than A since the straight line on graph for B has greater slope than that for A.
(iv) B overtook A at the instant when both were at the same place. This position is at the point where the two straight lines meet each other. For this point, distance from the starting point is 20 km and time is 4 h. Thus B overtook A when A has travelled for 4 h (or B has travelled for 4 - 2 = 2 h) at distance 20 km from the starting point