Question

A driver travelling at 60kmph applied brakes. The car decelerated uniformly and stopped in 5 seconds. Another driver going at 20kmph applied brakes slowly and stopped in 10 seconds. Plot speed vs time graphs on the same graph paper of the two cars. Which car travelled further after the drivers braked.

Answer 1

$\huge\pink{ Answer}$

(A) : Initial speed of the car A. u = 52 kmh-¹

$52 \times \frac{5}{18} = 14.44ms^{ - 1}$

The car stops in 5 seconds i.e V = 0 at T = 5

(A) : Initial speed of the car A U = 3kmh-¹

$= 3 \times \frac{5}{18} = 0.83 \: ms^{ - 1}$

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

$xb = \frac{1}{2} \times 14.44\times 5 = 36.1m$

∴ Distance covered by car A

$xb = \frac{1}{2} \times 0.83 \times 10 = 4.15m$

Thus car A travels more distance than B.