A 0.5 kg ball moving with a speed of 12 m/s strikes a hard wall at an angle of 30° with the wall. It is reflected with the same speed and at the same angle. If the ball is in contact with the wall for 0.25 s, the average force acting on the wall is:

24 N

Force will act along normal of the surface.

Initial Momentum along normal of the surface is $P_i = mvsin30^o = 3Kg-m/s$

Final Momentum along normal of the surface is $P_f = -mvsin30^o = -3Kg-m/s$

$\Delta P = P_f - P_i = 2mvsin30^o$

From Newton's Second law of Motion

F = \(\frac{ΔP}{Δt}\) = \(\frac{2mvsin30^o}{0.25}\) = 24 N