Why can’t you switch seats on an empty plane?

It’s the last Today’s flight and the plane is very empty. So, you’re thinking you’ll move up just a few rows, where there’s a nice window seat with an unobstructed view of the suite.

Not so fast. The flight attendant says this is a no-go. You must stay in your assigned seat or you will mess up the weight distribution in the plane. truly? Could animating a single life-sized human make a difference? Yes, you know where this is going: answering this question requires a bunch of cool physics. So let’s get to it!

MAS Center

People often say that the center of mass of an object is the location where all gravitational forces act. This is a good working definition, and you can use it to solve many physics problems, but it is not really correct. In fact, the force of gravity pulls everyone Parts of an object, not just a single point.

(Quick side note: We’re actually going to take a look at… center of gravitynot the center of mass, but in a constant gravitational field as here on Earth, they are the same.)

If you really want to understand center of mass, you have to consider torque. If we look at Newton’s second law, it states that the resultant force changes the motion of a body (F_network = mass x acceleration). So, if the net force is zero, the motion of the object will not change. If it is moving at a certain speed, it will continue to do so. If he is at rest, he will continue to rest.

Here’s a little experiment: Place a pencil on a flat table and then, using your index fingers, push it from opposite sides to the exact middle. It just stays there, right? Since you are acting with equal and opposite forces, the net force is zero. But what if you press it this way:

carrierIllustration: Rhett Allen