# WHAT is force? We know the physical applications of a force but WHAT is it?

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WHAT is force? We know the physical applications of a force but WHAT is it?

In: Physics

At some point the question becomes philosophical, or else circular with respect to our physical laws. Force is that which causes anything with mass to accelerate.

Force is one of those things in our universe that only makes sense when we see how it affects things. Another such thing is time.

I know it’s not a satisfying answer, but that’s metaphysics for you. Force is just a measurement of how much something changes its velocity compared to its internal energy.

Energy basically but in different forms, kinetic for instance. You push a cart. Your muscles put pushing energy into the cart and that starts moving.

“Force” isn’t necessarily a physical thing. It’s mostly just a mathematical concept to describe the change in momentum over time caused by two bodies interacting.

A force is something that pushes or pulls on an object and makes it move.

If you have a wagon [like this](https://www.radioflyer.com/media/catalog/product/cache/6fc979677405d10321ecd57e3744ab8a/b/i/big-red-classic-atw-inset-storage-model-1800_1.jpg), grab the handle and start walking, the force is the “oomph” you’re putting in to make the wagon start rolling.

Technically, a force can only *change* the motion of a thing, making it speed up, slow down, and/or change direction. Once the wagon’s rolling, it will keep going until something pushes it backwards to stop it.

(If you actually try this with a wagon, you’ll see the wagon will eventually stop. That’s because the air and the ground push backward on the wagon a little bit as it travels, and also the parts that turn stick very slightly to the parts that don’t, even if they’ve been well oiled. Usually scientists think of these small backward pushes together as being caused by a single backward-pushing force labeled “friction.”)