So, work is equal to force times distance. and we learned in the mechanical advantage etc. that the work in is equal to work out right? the force times the distance you put into a system is equal to the force times the distance you put out of it. and you migh want to review the work chapter for that but that's just the law of conservation of energy because work in is just the energy that you're putting into a system it's measured in joules and work out is just the energy that comes out of a system.