given that
mass of ball = 0.095 kg
initial velocity of ball towards the wall = 40 m/s
final velocity of the ball after it rebound = 30 m/s
now change in momentum is given as
[tex]\Delta P = m(v_f - v_i)[/tex]
[tex]\Delta P = 0.095(30 - (-40))[/tex]
[tex]\Delta P = 6.65 kg m/s[/tex]
So change in momentum will be 6.65 kg m/s