A child is sitting quietly on a swing. The child and the baby weigh a total of 16 kg. You throw a ball 2.1 kg to the child, who receives it. This causes the swing to swing backwards. If remember turns until it has reached 15 cm higher than its lowest point, what was the speed of the ball in what it was received by the child? The ball had a direction straight along the horizontal. See away from friction and air resistance.