EXTREMELY HARD PHYSICS: Stacy runs at a speed of 5.0 m/s and dives onto a sled that is initially at rest?

Question

Stacy runs at a speed of 5.0 m/s and dives onto a sled that is initially at rest at the top of a frictionless snow-covered hill. After she and the sled have descended a vertical distance of 5 m, the hill levels out a big and her brother, who is initially at rest, jumps onto the sled and together they continue down the hill. What is their speed at the bottom of the hill if the total vetical drop is 16 m? Stacy's mass is 40kg, the sled is 5 kg, and her brother is 60kg.

Answer 1

first find initial velocity. turns out to be 4.44 m/s. i think you have to use energy. energy at top turns out to be mgh+.5mv^2, or 2649.44J with respect to when the brother jumps on. then use kinetic energy formula to get velocity right when the brother jumps on. turns out to be 10.85m/s. then use momentum again to get velocity after he jumps on. turns out to be 4.65m/s. then use energy again. turns out to be 12,454.48J with respect to the ground. then use kinetic energy formula again to get final velocity. turns out to be 15.4m/s. and you are done!!!

Answer 2

actually this is an easy example.Just draw the picture, label all stuff u have,and its all about trigonometry and forces.SInce its frictionless surface u dont consider the friction in the motion.
For the x motion u take the x component of the girls weight+x components for the guys weight,the normal forces .Since they gave u the y component ,the vertical drop. Theres a specific equation for that.I forgot. But dont forget to separate the motion into x and y components.