Linda runs at a speed of 4.0 m/s and dives on a sled, initially at rost on the top of a frictionless, snow- covered hill. After she has descended a vertical distance of 5.0 m, her brother, who is initially at rest, hops
on her back, and they continue down the hill together. What is their speed at the bottom of the hill if the
otal vertical drop is 15.0 m? Linda's mass is 50 kg, the sled has a mass of 5.0 kg, and her brother has a
mass of 30 kg