Assuming that the vectors are acting along the same axis, we
could just simply add or subtract the vectors. Since the F1 is greater than F2,
there would be motion, there would be acceleration, and that the direction of
motion is along the F1.
From that list, only the frequency makes the difference.
Einstein won his only Nobel Prize for his explanation of this effect.
Explanation:
Mass of the ball, m = 0.058 kg
Initial speed of the ball, u = 11 m/s
Final speed of the ball, v = -11 m/s (negative as it rebounds)
Time, t = 2.1 s
(a) Let F is the average force exerted on the wall. It is given by :


F = 0.607 N
(b) Area of wall, 
Let P is the average pressure on that area. It is given by :


P = 0.202 Pa
Hence, this is the required solution.