Question

A truck and a car are moving on a smooth, level road such that the kinetic energy associated with them is same. Brakes are applied simultaneously in both of them such that equal retarding forces are produced in them. 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

Answer: (C)

Both will cover the same distance

If both are moving with same kinetic energy then $m_1{v}_1^2=m_2{v}_2^2$

Now if acting force is same then $a_1=\frac{F}{m_1}$

And $a_2=\frac{F}{m_2}$

Distance travelled is $S=\frac{v^2}{2a}$

So $S_1=v_1^2\ast \frac{m_1}{2F}$

And $S_2=v_2^2\ast \frac{m_2}{2F}$

But we already knows that $m_1{v}_1^2=m_2{v}_2^2$

So distance travelled by both bodies is same.