For this problem, we need the famous F=ma equation, as described by Isaac Newton.
Force=mass x acceleration, where force is expressed in Newtons.
The velocity change of the ball is 20 m/s over a time step of 0.1 seconds. By dividing the velocity by the amount of time it takes to make the change, we can get acceleration; we need this new value, 200 m/s^2, instead of velocity for the equation.
F=(0.45 kg)(200 m/s^2)= 90 N of force.
