Force F$,$ acting in a constant direction on the block, has a magnitude which varies with the position $s$ of the block, $F=(50s^{0\mathrm{.}5})N.$ The mass of the block is $20$ kg $.$

When $s=0$ the block is moving to the right with speed $v=6\frac{m}{s}.$

The coefficient of kinetic friction between the block and the surface is ${}_k=0\mathrm{.}3.$

Answer the questions:

What is the work performed by friction force when $s=20m?(3$ points$)$

What is the work performed by force F when $s=20m?(3$ points$)$

What is the block's speed when $s=20m?($Apply the principle of work and energy.$)(4$ points$)$