Question

A truck and a car are moving on a smooth, level road such that the K.E. associated with them is same. Brakes are applied to both of them simultaneously. Which one will cover a greater distance before it stops ?

• A. Car
• B. Truck
• C. Both will cover the same distance
• D. Nothing can be decided

Answer 1

The correct option is A Car

Let the mass of truck be $M$ and velocity be $v_1$

And, the mass of car be $m$ and velocity be $v_2$

$M>m$

if kinetic energy is same;

$\frac{1}{2}M{v}_1^2=$ $\frac{1}{2}m{v}_2^2$

If break is applied, both goes in retardation $-a$

for truck, $x_1=\frac{v_1^2}{2a}$

for car, $x_2=\frac{v_2^2}{2a}$

Since, $v_2>v_1$

$x_2>x_1$

Hence car covers greater distance.