Given that the time is t = 10 s and the power is P = 50 W.
We have to find the work done.
The work done can be calculated by the formula
[tex]\begin{gathered} P\text{ =}\frac{W}{t} \\ W=P\times t \end{gathered}[/tex]Substituting the values, the work done will be
[tex]\begin{gathered} W\text{ = 50}\times10 \\ =500\text{ J} \end{gathered}[/tex]Thus, the work done will be 500 J
The work done when time t' = 9.5 s is
[tex]\begin{gathered} W^{\prime}=50\times9.5 \\ =475\text{ J} \end{gathered}[/tex]The less work done will be W-W' = 500-475 = 25 J
Sprinter has to do 25 J less work.