This weekend I was trying to calculate the work-energy theorem, considering a body that can be treated like a particle, and has its mass varying in time. I searched through a lot of sites if such thing existed, and didn´t find anything. Then I found a thread (https://www.physicsforums.com/threads/work-energy-theorem-for-variable-mass-systems.720649/) from 2013, asking that same thing, but appeared to not be answered. This motivated me to put my results in here. As I´m not familiarized with writing the math in the computer, I put the image of how I did it below. Summarizing, I found this equation: dW = dK + (1/2)v2dm Where W stands for the work done by the net force F, K stands for kinectic energy, m stands for mass in function of time, and v stands for the norm of the velocity. http://imgur.com/a/MUhaT Is this result correct? If not, where did I go wrong?