When 5.0MJ of energy is supplied as heat to an isolated metal block, which statement best describes what happens to the block’s total rest mass?
(a) It decreases by a small amount equal to E/c2, because energy replaces mass.
(b) It remains unchanged; the block’s rest mass is invariant and only its relativistic mass could change.
(c) It increases by a very small amount Δm=E/c2. (Correct)
(d) It increases by a small amount Δm=E/c owing to the added energy.