Question

How fast should a man weighing $600N$ needs to run, so that his kinetic energy is $750J$? Take $g=10m{s}^{-2}$

• A. $3m{s}^{-1}$
• B. $4m{s}^{-1}$
• C. $5m{s}^{-1}$
• D. $6m{s}^{-1}$

Answer 1

The correct option is C

$5m{s}^{-1}$

Given, the weight of a man, $W=600N$, $g=10m{s}^{-2}$, kinetic energy, $KE=750J$
Let the mass of the man be $m$ and the velocity be $v$.
We know, $W=mg$
So, $600=m\times 10$
On solving we get, $m=60kg$
As we know, $KE=\frac{1}{2}m{v}^2$
So, $750=\frac{1}{2}\times 60\times v^2$
or, $v=5m{s}^{-1}$