As the ball falls from a height to the floor, the gravitational potential energy stored in the ball will be converted to kinetic energy.The gravitational potential energy of the ball can be calculated using:gpe = mgh : m =0.8kg, g=9.8N/kg, h=5m so gpe = 0.8 x 9.8 x 5 = 39.2JKinetic energy can be calculated using: eK = 0.5 x m x v^2 . We can rearrange this to get v = SqRt (( 2 x eK )/ m).eK = 39.2J, m=0.8kg, so v = SqRt ((2 x 39.2)/0.8) = 9.899 m/s. To 2sf this is 9.9m/s