What is the force exerted on a wall when a ball weighing 500g traveling at 10 m/s bounces off the wall.

The force extend on the wall by the ball is reacted with
an equal but opposite force in accordance with the 3rd law of  motion
.

So the mass of the ball =  500g. = 1/2
kg.

Velocity of the ball =
10m/sec.

Time or duration the  in which thel ball lost its
velocity to zero is   say  t secs. (But here the information of time is not
given)

Therefore the acceleration  (in this case retrdation
) of the ball  = (10m/s)t s = (10/t)m/s^2

Therefore the
force  = ma = ((1/2)Kg * (10/t)m/s^2 = (5/t) Newton is exerted on the wall by the
ball.