Q. 54

# The speed-time graph for a car is shown is Fig. 8.12.

(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) Distance travelled by car in the 4 seconds**

The area under the slope of the speed – time graph gives the distance travelled by an object.

In the given graph

56 full squares and 12 half squares come under the area slope for the time of 4 second.

Total number of squares = 56 + 12/2 = 62 squares

The total area of the squares will give the distance travelled by the car in 4 second.

On the time axis, 5 squares = 2s

∴ 1 square =25s=25s

On the speed asix 3 squares = 2 m/s

∴ 1 square =23m/s=23m/s

∴ area of 1 square =25s×23m/s=415m=25s×23m/s=415m

∴ area of 62 squares =415m×62=415m×62

24815m=16.53m24815m=16.53m

Therefore, car travels 16.53 m in first 4 second.

(b) Part MN of the slope of the graph is straight line parallel to the time axis, thus this potion of graph represents uniform motion of car.

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