The average force exerted on the football is 100 Newtons.
To find the average force exerted on the football, we can use the equation:
Favg = m * Δv / Δt
Where m is the mass of the football, Δv is the change in velocity, and Δt is the time interval. In this case, the mass of the football is 0.1 kg and the change in velocity is 20.0 m/s (final velocity - initial velocity). We also know that the time interval is 20.0 ms, which is equivalent to 0.020 s.
Substituting the known values into the equation, we get:
Favg = 0.1 kg * (20.0 m/s) / 0.020 s = 100 N
Therefore, the average force exerted on the football to give it a velocity of 20.0 m/s is 100 Newtons.