The work originally done on this rock while it was being thrown upwards is going to equal the change in its kinetic energy. It initially has some kinetic energy and changes to zero when it gets to the top of its path and the work that gravity has to do to create that change in kinetic energy is the force of gravity times the height that it goes. So we can solve for ‘h’ and that’s going to be the work done on it originally which is the change in kinetic energy divided by the force of gravity ‘mg’. So that’s 80 Jules divided by 1.85 kilograms times 9.8 Newtons per kilogram. This equals ANSWER meters.