Question

A retarding force is applied to stop a motar car.if the speed of the motar car is doubled,how much more distance will it cover before stopping under the same retarding force?

Answer 1

Let the speed of the motor car be v.

Force needed to stop the car be F.

Let the acceleration be a and mass be m

F = ma

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

$s_1 = \frac{v^2}{2a}$

Now, the speed is doubled.

Hence, the speed is 2v

Now,

$s_2 = \frac{(2v)^2}{2a}$

$s_2 = 4s_1$

Hence, the motor car will cover three times more distance when the speed is doubled.