Answer:
[tex]147.653J = W_f[/tex]
Explanation:
We know that:
[tex]E_i - E_f = W_f[/tex]
where [tex]E_i[/tex] is the initial energy, [tex]E_f[/tex] is the final energy and [tex]W_f[/tex] is the energy lost due to friction.
so:
[tex]\frac{1}{2}MV^2-0 = W_f[/tex]
Where M is the mass and V is the velocity of the runner, so:
[tex]\frac{1}{2}(68.2kg)(4.33m/s)^2 = W_f[/tex]
[tex]147.653J = W_f[/tex]