A 5.0 kg medicine ball and a 7.0 kg medicine ball are the same size and shape. If you were in outer space, how would you determine which ball had which mass?
I need to calculate this somehow. Help? Thanks!

Two kilograms of air within a piston–cylinder assembly executes a carnot power cycle with maximum and minimum temperatures of 800 k and 300 k, respectively. the heat transfer to the air during the isothermal expansion is 60 kj. at the end of the isothermal expansion the volume is 0.4 m3. assume the ideal gas model for the air. determine the thermal efficiency, the volume at the beginning of the isothermal expansion, in m3, and the work during the adiabatic expansion, in kj.