How is inertia and momentum important in football?

Answer 1

Inertia and Momentum in FootballInertia is a mass's resistance to changes in its momentum. Objects that have greater mass have greater inertia, so they are more difficult to move when they are at rest and more difficult to stop when they are moving.

A 320-pound NFL nose-tackle has lots of inertia. A runt like me who weighs a buck fifty and change, not so much. The nose-tackle is gonna be hard to move out of the way, so blocking him will be difficult. And if a running back carrying the ball runs into him, the play might end right then and there. If he ran into me, well, let's say that he would easily overcome my inertia, knock me into next week, and take it to the house.

Which brings us to momentum. Momentum is also related to mass, but it is also related to velocity. If an object is at rest, it has zero momentum. A moving object, however, has momentum. Double the speed and you double the mo. Triple the speed, triple the mo. If a running back runs fast, he will build up momentum. He can use that momentum to overcome another player's inertia. If he runs into the nose-tackle, he'll need lotsa mo to overcome his inertia. If he runs into me, he won't need much.

Just to complicate this a bit, an object with momentum has kinetic energy, and energy can be used to do work. To do work you must apply a force, and it's that force that can change another object's momentum. Since mass can't change, it stands to reason that velocity must change. So when the running back picks up a head of steam and plows into me, he's gonna change my momentum in a big way. I'm gonna go flying like a little kid's rag doll.