Chapter 7

NCERT
Class 9
Science
Solutions
8. The speed time graph for a car is shown in the figure.

Question:

The speed time graph for a car is shown in the figure.

(a) Find how far does the car travel in the first 4 seconds. Shade the area on the graph that represents the distance travelled by the car during the period.

(b) Which part of the graph represents uniform motion of the car?

Answer:

(a) Here, 4 squares on t-axis = 4s

1 squares = 1s

2 squares on v-axis = 2 ms–1

1 squares = 1 ms–1

Hence area of 1 square = 1 × 1 = 1 m from t = 0 to t = 4s, the number of squares of the region between the v-t graph and t-axis = n = 20 (more than half the squares have been considered).

Hence the distance covered by the car is 13.33 m through the dotted squares.

(b) Here the speed of car is uniform after t = 7 seconds.

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