Question

A truck and a car are moving with equal velocity; on applying brakes, both will stop after a certain distance, then:

• A. truck will cover less distance before stopping
• B. car will cover less distance before stopping
• C. both will cover equal distance
• D. none

Answer 1

The correct option is B car will cover less distance before stopping

On applying brake $F=ma$, Truck has more mass than car so acceleration of truck is less than car,

$\Rightarrow a_{Car}>a_{Truck}$ ....1

Let initial velocity is $u$, Final velocity $v=0$, Distance travelled by car= $S_{Car}$ and by Truck= $S_{Truck}$.

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

$\Rightarrow 0=u^2-2\times a_{Car}{S}_{Car}$ $\Rightarrow S_{Car}=\frac{u^2}{2a_{Car}}$ .....2

$\Rightarrow 0=u^2-2\times a_{Truck}{S}_{Truck}$ $\Rightarrow S_{Truck}=\frac{u^2}{2a_{Truck}}$ .....3

Dividing equation 2 by 3,

$\frac{S_{Car}}{S_{Truck}}=\frac{a_{Truck}}{a_{Car}}$<1 (Using Equation 1)

So car will cover less distance before stopping.