Q. Gayle runs at a speed of 4m/s and dives on a sled, initially at rest on the top of a frictionless snow covered hill. After she has descended a vertical distance of 5m, her brother, who is initially at rest, hops on her back and together they continue down the hill. What is their speed at the bottom of the hill if total vertical drop is 15 m? Gayle's mass is 50kg, the sled has a mass of 5kg and her brother has a mass of 30kg.