How do you tell apart in space 2 identical boxes one filled with heavy metal parts and the other with light plastic parts without opening the boxes up?

Answer 1

Since you are in space, weighing them doesn't help you, because both of them

register zero on the bathroom scale.

You know that the box of metal parts has more mass, because it's heavier on

Earth. And the one with plastic parts has less mass, because it's lighter on Earth.

So you can perform an experiment to find out which box has more mass.

Since you are already in space, we can assume that you not only have the

physical attributes required of an astronaut, but that you are a hot-shot

intellectual as well, with a vast background in science and engineering. So

you know that [ F = M A ], and at last, you have a chance to use that arcane

knowledge!

You quickly solve Newton's equation for 'A' in your head, and get [ A = F/M ].

That tells you that when different masses are subjected to equal forces, their

acceleration is inversely proportional to their mass. The beauty of it in this

situation is that it's true anywhere, whether you're sitting on a planet or

floating in space.

So you quickly hang both identical boxes in the air in front of you, put one hand

against each box, put your back against the bulkhead, and push both boxes

with small, equal forces. The actual size of the force doesn't matter, as long as

the forces of both hands are equal.

Slowly the boxes begin to move away from you, and just as you had hoped, one

of them pulls out ahead of the other one almost immediately, and its lead keeps

building. That's obviously the one with greater acceleration, therefore less mass,

and therefore the one with the plastic parts inside.

You have no time to contemplate your discovery, however, because both boxes

are now beyond the end of your arms and still going, straight toward the two

guys in the flight-control seats at the other end of the flight deck, fast asleep in

their harnesses with their backs to you. You yell "FORE!", and then with rising

panic, try to figure out some way to arrest the sailing cargo crates. From your

vast astronaut training, you know it won't do you any good to push yourself off

the bulkhead and overtake them, because although you can easily overtake them,

you'll have no way to stop them once you get there.

You brought me aboard to help you identify the contents of the unmarked crates,

which I've done, and my work here is finished. I must leave now, and I hope you

figure out a way to get ahold of the crates and nail them down, before they go

through the window.

Good luck, champ. Have a nice day.

Answer 2

You can differentiate the boxes by using a scale or testing their weight. The box with heavy metal parts will weigh more than the box with light plastic parts, allowing you to identify which box contains which material without opening them up.