Question

A car P traveling at 90 km h-1 and is stopped by the application of brakes in 6 s. Another car Q traveling at 54 km h-1 is stopped by the application of brakes in 10 s. Plot the motion of cars P and Q on the same graph paper and then calculate which car travels farther and by how much.

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.