A ball flies through the air, hits the ground, and bounces back up. You can choose a soccer ball, basketball, or volleyball, and select the initial velocity, angle of incidence, and angle of rebound to determine the forces on the ball when it hits the ground. The coefficient of restitution for each type of ball is estimated as 0.8, which means that the vertical velocity is reduced by 20% after impact with the ground. Frictional forces also reduce the horizontal velocity of the ball. The frictional and normal forces are found from the input values, using the change of momentum component with time , .