Homework Question-Help Please! I feel kind of silly because this is probably a very basic problem, but I'm having problems with physics in general. Would anyone be able to tell me if I'm on the right track for the following question (we are focusing on Einstein's theories of relativity right now)? 1. Is the mass of a frying pan different when it is hot compared to when it is cold? Yes it is, as E=mc^2 proves. Because the mass is equivalent to the energy of the object, when the energy increases, so does the mass. As energy increases when an object is heated, the mass of the pan will also increase when it is heated. The mass will decrease when the pan is cool and the energy has decreased. ~~ I hope I have this right. Lately I feel very hopeless at physics. Any help or comment would be very much appreciated.