A 2.2 kg rock is released from rest at the surface of a pond 1.8 m deep. As the rock falls, a constant upward force of 5.0 N is exerted on it by water resistance. Let y=0 be at the bottom of the pond. Calculate the nonconservative work, Wnc , done by water resistance on the rock, the gravitational potential energy of the system, U , the kinetic energy of the rock, K , and the total mechanical energy of the system, E , when the depth of the rock below the water's surface is 0 m.

2 answers

When the depth of the rock below the surface is 0 m, it has not moved since it was released at the surface. No work has been done and there is zero kintic energy.

Are you sure you copied the last line coreectly?
There are 3 portions. The next one is at 0.50 m and the last one is when the rock is at 1.0 m.