Answer:
The loss in mechanical energy is 668.25 J
Step-by-step explanation:
As per the question:
Mass of the base runner, m = 66 kg
Velocity of the runner, v = 4.5 m/s
Coefficient of friction,

Now,
The mechanical energy lost due to friction is provided by the work done in the form of the Kinetic energy of the runner:
Work done, W = Kinetic enrgy of the runner
W =

W =

Work done must be - 668.25 J as the runner slows down.