Question

A force 'F' stops a body body of mass 'm' moving with a velocity 'u' in a distance 's'.The force required to stop a body of double the mass moving with double the velocity in the same distance is:

• A. 4F
• B. 5F
• C. 2F
• D. 8F

Answer 1

The correct option is C 2F

First case

Apply energy conservation theorem

$△w=△kE$

$F.d=\frac{1}{2}m{v}^2-\frac{1}{2}m{v}^2=0-\frac{1}{2}m{v}^2$

$FS=-\frac{1}{2}m{v}^2$ __(1)

Second case

$△w=△KE$

$F^1.d=0-\frac{1}{2}\left(2m\right)v^2$

$F^{1}d=-m{v}^2$

From equation (i)

$F^1.d=2F.S$

Now

$d=S$

$F^1=2F$