Question

Uniform constant retarding force is applied in order to stop a truck. If its speed is doubled then the distance travelled by it will be

• A. four times
• B. double
• C. half
• D. same

Answer 1

The correct option is A four times

We know that $s=\frac{-(v^2-u^2)}{2a}$ (negative sign for retarding force.)
Since force is constant, thus acceleration is constant.
In first case with speed u, it stops when v=0, thus $s=\frac{-(0-u^2)}{2a}=\frac{u^2}{2a}$
In second case with speed = 2u, $s=\frac{-(0-{\left(2u\right)}^2)}{2a}=\frac{4u^2}{2a}$
Thus it is 4 times