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?

The objects can be distinguished by their weight instead of by mass.

Explanation

Because mass is constant, the two objects cannot be distinguished by mass.

However, gravitational acceleration varies in outer space. Therefore the heavier mass will register a higher reading on a weighing scale.

Note that an object of mass M weighs Mg, where g = acceleration due to gravity.