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: 
I think maybe you are confused by an example that is often given to emphasize that the physics definition of "work" doesn't always match how it is used in everyday speech. If you move a rock *horizontally* at constant speed, then you are doing no work on the rock. Its kinetic and potential energy are both the same through the whole process. This is a common example because it certainly feels like you are doing work, and that is because maintaining constant tension in your muscles takes energy, which is converted into heat. Individual cells contract and then get tired and loosen up; you can't just lock your muscle at a certain length.

But lifting a rock upward is different, even if the velocity is constant. Then you really are doing work on it in the physics sense, because you are converting chemical energy to gravitational potential energy.
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.