## Chapter 7

NCERT
Class 9
Science
Solutions

### Question:

Figure shows the distance-time graph of three objects A, B and C. Study the graph and answer the following questions.

(a) Which of the three is travelling the fastest?

(b) Are all three ever at the some point on the road?

(c) How far has C travelled when B passes A?

(d) How far has B travelled by the time it passes C?

(a) The value of velocity is greater when inclination of x-t graph from the time-axis is greater. The inclination of x-t graph of object B is the highest so B is moving at the fastest speed.

(b) All three x-t graph do not meet at any one point. Hence A, B and C will never be at the same point on the road.

(c) B overtakes A at 0.7 h. It is clear from the x-t graph of C that the position of C at t = 0.7h is x = 15 km.

Initial position of C (at t = 0) x = 8 km

Hence, the distance covered by C from t = 0 to t = 0.7 h is = 15 km – 8 km = 7 km

(d) The value of time of B passing through C is t = 1 h at t = 1 h, the position of B is 18 km at t = 0, The position of B is 0.

Hence the distance covered by B from t = 0 to t = 1 h is = 18 – 0 = 18 km.