Gayle runs at a speed of 9.00 m/s and dives on a sled, initially at rest on the top of a frictionless, snow-covered hill, that has a vertical drop of 20.0 m. After she has descended a vertical distance of 4.00 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?

Question

Gayle runs at a speed of 9.00 m/s and dives on a sled, initially at rest on the top of a frictionless, snow-covered hill, that has a vertical drop of 20.0 m. After she has descended a vertical distance of 4.00 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?
Gayle’s mass is 70.0 kg, the sled has a mass of 2.00 kg, and her brother has a mass of 50.0 kg.

bobpursley · Answer

energies gained=final energy

HerPE+HisPE+herinitalKE+hisInitialKE= finalcombinedKE + finalPE

+G*9.8*20+B*9.8*16 +1/2 G 9^2+ 0=1/2 (G+B)Vf^2+0

G is her mass, B is brothers mass, Vf is the finalspeed at bottom.
check my thinking.

Anonymous · Answer

I don't think I am getting the right value, what are you getting?