Question: A previous post ([What Is Energy? Where did it come from?](https://physics.stackexchange.com/q/3014/)) defines work qualitatively as "a process in which energy is transformed from one form to another form". And mathematically, work is defined as:

$$\Delta KE=\int\_{C} \vec{F}\cdot\mathrm d\vec{r}$$

But if you imagine lifting up a rock from the ground at constant speed, am I not doing work on the rock by converting the chemical energy stored in my muscles into the potential energy of the rock? I am confused because the kinetic energy of the rock does not change and yet I am still converting energy from one form to another, which is the qualitative definition of work. What's the right way to think about this and the concept of work in general?

Answer: 
Assume you have two opposite forces of the same magnitude acting on a particle. The total work is zero, and there is no change in kinetic energy. However one of the forces made positive work on the particle and the other negative work. Whatever did positive work lost some form of energy, and the one that did negative work won some energy. The net effect on the particle is zero, but there was an exchange of energy between two systems, the ones which generated the forces.
Alternatively, if one of the forces is dissipative, like friction, some energy will be dissipated as heat.
My professor explained it to me by giving me the spring example.

Suppose there is a spring attached to a block of mass m at one end and wall at the other.Neglect friction everywhere.

If we now pull the mass with constant velocity. Let's us see what changes happens:

In the above example there are 3 objects that are me pulling the block , the block , and the spring.

Now since we pull block with constant velocity Net force on it 0. But since the spring is attached to the block it's potential energy increases. Now we generally treat mass and spring as a system hence potential energy of system increases.

In your case block and earth = spring and mass .In your case the potential energy of block is stored between mutual gravitational field of block and earth.
You applying the force is a constant variable.

I hope it makes sense.