Alright, I was wondering if Change in Kinetic energy of a particle (after undergoing a constant force acting on it) would be oberserved to be the different value measured from two different inertial reference frames. Here's one particular case...Say you're on earth and I on a space ship. We are both observing the same particle in the space and there's a force action on the particale. The partical displace it self through surface, therefore there's work done on the particle due to the force and therefore it will change it's kinetic energy. But, would that change in kinetic energy of the partical agree if you were to do the same calculation from the spaceship?