Answer:
Average force on the football = 168.82 N
Explanation:
Force = Mass x Acceleration
F = ma
Mass, m = 0.41 kg
We have equation of motion, v = u + at
Initial velocity, u = 0 m/s
Final velocity, v = 21 m/s
Time, t = 0.051 s
Substituting
         21 = 0 + a x 0.051
           a = 411.76 m/s²
Substituting in force equation,
          F = ma = 0.41 x 411.76 = 168.82 N
Average force on the football = 168.82 N