Question

A truck and a car are moving with equal velocity. If equal retarding force is applied to each of them on applying the brakes, both will stop after a certain distance. Then

• A. Truck will cover less distance before rest
• B. Car will cover less distance before rest
• C. Both will cover equal distance
• D. Cannot be determined

Answer 1

The correct option is B Car will cover less distance before rest

Using 3rd equation of motion,
$v^2-u^2=2as$

Putting $v=0$,
$u^2=2as$ (negative sign in $a$ cancels negative sign with $u$)

And putting $a=\frac{f}{m}$, where $f$ is retarding force
Stopping distance $s=\frac{u^{2}m}{2f}$
The mass of the truck is greater than that of the car. Hence when velocity is the same, then the car will cover less distance as the stopping distance is directly proportional to mass.
Hence, the correct option is (b).