You Need to Weigh Some Water. All You’ve Got Is a Paper Clip

Let’s suppose you need to measure the mass of some water, and you want to construct a scale to do it. But you are in a normal house filled with normal stuff. There’s no fancy scientific equipment. Can you do it with a common household item?

I think this is indeed possible, and I’m going to try to do it—with a paper clip.

OK, but why? This started with my work as the technical consultant for the CBS show MacGyver. My job was to check the scientific plausibility of different hacks and sometimes suggest ways that MacGyver could get out of a tricky situation. One of MacGyver’s favorite things to use was a paper clip—so I figured I would see how many things I could make from them.

So far, I’ve made some cool paper clip-based gadgets.

It’s just fun making complicated objects from basic parts—it’s the MacGyver way.

Now for the scale. This might seem simple, but there’s going to be some graphing involved, such that this might be more appropriate as a blog post instead of a video. Let’s do it.

Remember, the goal here is to measure the mass of some water. Since we are on the surface of the Earth, there is a constant relationship between mass and weight—so we are technically going to measure the water’s weight. What’s the difference between mass and weight? Here is my full explanation, but the short answer is that mass is the amount of matter (protons, neutrons, electrons) a thing is made of, and weight is the gravitational force exerted on that object by the Earth.

So how do you measure weight? It turns out that most of our measurement tools are actually for measuring distance. (It’s true—check it out.) In this case, we can determine the weight (and thus the mass) of something by measuring the deflection of a paper clip, or how much it bends. If you have straightened a paper clip out into a long wire, the more you push on one end, the more it bends. However, when it’s curled up into its normal paper clip shape, it is much more difficult to fold. This is very similar to the force required to stretch a spring, which is much harder to deform than a straight wire. However, for an ideal spring, the stretch distance is linearly proportional to the stretching force, and that might not be true with a bending paper clip.

So the idea is that if we flatten out our paper clip, we can turn it into a lever arm that will help us weigh our water.

Let’s build this thing. Here is what I have.