Question

A car travelling at 30 mph takes 10 m to come to a complete stop. Consider the work done by the brakes when stopping to estimate the distance required to bring the car to a complete stop from 75 mph. What is this distance

Answer 1

Answer:

The value of the distance S = 62.5 m

Explanation:

From third law of motion

$v^{2} = u^{2} + 2 as$

v = 0 & u = 30

So 0 = $30^{2}$ + 2 × a × 10

a = - 45 $\frac{m}{s^{2} }$

When the car speed is 75 $\frac{mi}{hr}$  then in that case

u =  75 $\frac{mi}{hr}$ , v = 0

$v^{2} = u^{2} + 2 as$

$75^{2} = - 2 a S$

$S = \frac{75^{2} }{-2 (-45)}$

S = 62.5 m

This is the value of the distance.