The gravitational force you experience on earth not only varies based on...
So I certainly understand your concern but it won't matter for everyday people and in experiments the proper unit can be used.
The joule is a unit if energy, and since E=mc^2 related mass and energy you...
So it'd look like this unsolved
(E=h(hz value from kyle's video))=mc^2, so once you get the energy value using kyle's plug in you then just have to divide by c^2 on both sides and you get the answer. m is 1kg...