Avinash can run with a speed of $8\ ms^{-1}$ against the frictional force of $10\ N$, and Kapil can move with a speed of $3\ ms^{-1}$ against the frictional force of $25\ N$. Who is more powerful and why?

We know $P=Fv$

Here, $P\rightarrow$power

$F\rightarrow$force

$v\rightarrow$speed

For Avinash:

Speed of Avinash $v_{A}=8\ ms^{-1}$

Force of friction $F_A=10\ N$

So, power of Avinash, $P_A=F_A.v_A=10\ N\times8\ ms^{-1}=80\ W$

For Kapil:

Speed of Kapil $v_{K}=3\ ms^{-1}$

Force of friction $F_K=25\ N$

So, power of Kapil, $P_K=F_K.v_K=25\ N\times3\ ms^{-1}=75\ W$

On comparing powers of both, $P_K$<$P_A$

 So, Avinash is more powerfull.