Question

un and speed
10. Adriver of a car travelling at 52 km/h. applies the brakes and decelerates uniformly. The car
stops in 5 seconds. Another driver going at 34 km/h, applies his brakes slower and stops
after 10 seconds. On the same graph paper plot the speed-time graph for two cars. Which of
the two cars travelled farther after the brakes were applied?​

Answer 1

answer

(A) : Initial speed of the car A u=52 kmh

−1

=52×

18

5

=14.44 ms

−1

The car stops in 5 seconds i.e v=0 at t=5

(A) : Initial speed of the car A u=3 kmh

−1

=3×

18

5

=0.83 ms

−1

The car stops in 10 seconds i.e v=0 at t=10

With the help of these initial and final points for both the cases, we can plot the graph of speed vs time.

Area under the speed-time graph gives the distance covered.

∴ Distance covered by car A x

A

=

2

1

×14.44×5=36.1 m

∴ Distance covered by car A x

B

=

2

1

×0.83×10=4.15 m

Thus car A travels more distance than B.

solution