July 16, 2020

How to Measure Pressure With a Phone and a Baggie

This states tension is just power (F) per device of area (A). If the drive is calculated in newtons and the spot is in square meters, then the pressure would be in models of N/m2, which is called a pascal. But you can use other models also, like lbs . per sq. inch or atmospheres (1 atm is about 105 pascals).

As you can see, if the mass on leading of the bag stays the exact, so that the gravitational pressure F is unchanged, but the space decreases, then the force would have to enhance. Is that legit? That is what’s so fantastic about this experiment—you can verify the results by yourself.

Could You Use It As a Scale?

Now how about one thing more complicated? Given the relationship between the mass on top rated and the air tension inside, could you use this barometer-in-a-bag set up to evaluate the mass of anything? I think it will operate. (Technically it would measure the bodyweight of the item, not the mass.) Here is what I’m likely to do:

  • Get started with just the Lego system on best and report the stress.
  • Put a new item, of unfamiliar weight, on prime.
  • File the new stress. It is really this transform in tension we want.
  • Following, make the Lego system smaller and repeat.

Maybe it will assist if I rewrite the pressure equation like this:

Illustration: Rhett Allain

If I plot stress on the vertical axis and 1/A on the horizontal axis, then this need to look just like the equation for a line with the power as the slope. OK—let’s do it. Oh hold out! What about the place of the Lego platform? In this circumstance, I used multiple bricks of the similar size (.96 x 3.18 cm) so that I could just take away a brick and lower the floor location by a identified volume. Yes, Lego parts are very uniform in dimension.

Hmm … that was my strategy, but it did not function. The force in the bag ought to enhance when I swap in the scaled-down Lego platform, but it failed to. I actually assume my bag could be leaking. No make any difference, this experiment is for you to do at dwelling. See if you can make it get the job done.

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