(Physics 1 help) I do not understand part B of this problem:

Question

James Bond is running with a speed of 10 m/s:

a) How much kinetic energy does James Bond have if his mass is 85kg?

b) If he grabs onto a 15m rope that is hanging from the ceiling while he runs and swings upwards, how high off the ground will he swing?

Answer 1

a) The Kinetic Energy of the running man is (.5)(85 kg)(10m/s)² = 4250 kg-m²/s²)

b) At the top height of the man as he swings on the rope, his velocity = 0. So the total energy at that point is just the the potential energy since there is no kinetic energy at this point.

So, potential energy = mgh = 4250 kg-m²/s² and h = 4250/(85)(9.8) = 5.1 m

In these calculations, the reference is the mass center of the man.