Objects in Water as an Example of Newton’s Third Law
This is maybe one of my favorite physics demonstrations showing both the buoyancy force and Newton’s third law. You can start it off as the following question:
Imagine I have a beaker of water on a scale that reads 4.06 Newtons (most scales you can switch to display units of Newtons instead of grams). What will happen to the scale reading if I lower a metal cylinder into the water (but still hanging from a support)? Will the scale reading go down, stay the same, or go up?
Go ahead and consider this question. I’ll wait. Here’s a picture of a dog and a flower (while you think).
I’m going to show you the answer (of course), but let’s review some physics first. I want to go over two things: Newton’s third law and buoyancy.
Newton’s Third Law
I really think that we focus on the “three laws” too much. But no one listens to me. They are essentially a way to describe interactions as a force and the consequence of having a net force on an object. The third law should go something like this:
Forces are an interaction between two objects. If object A pushes on…
