What does f ma mean in physics

Mike W. Intuitively it makes sense but is it all just experimental? I hope you'll forgive a long-winded, fuzzy answer, since I don't know any good short answer. Here's the problem. Most objects don't come stamped with an "m" value on them. Space and time aren't laid out with a labeled grid of coordinates, so we aren't just given the " a " values for objects. Worst of all, what's F? Let's say we ignore the question of how to determine a , by assuming that somehow we have a common-sense set of space-time coordinates that we're happy with.

We can bounce objects off each other, and by measuring their velocities before and after the bounce, figure out the ratios of their m's. Pick one object to call the unit mass, and now we have a set of m's. Now we get to the hard part. What are the F 's? Let's say we see some m with an a. So we must insist on some rules about the F 's. The third law says that there needs to be an opposite F on something else, and we can insist that the something else is fairly nearby. More generally, we can insist that the rules for when there should be an F shouldn't be too weird or complicated.

Up to a point, that program works. That's a very compressed version of a long discussion. Feel free to follow up. It seems like this is what Mr. Newton did while experimenting on accelerating objects before he came up with this law, but since he was the head of the British Royal Society of science, no one dared question him.

It doesn't have to take an Einstein to realize that, but a willing to be disattached from prejudices. I hope no one gets offended by my questioning as if I attacked their religious beliefs. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

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It also seems to describe the world around us pretty well. I don't know what you want. We seek a set of rules that allow us to correctly describe the world. And while we have some very powerful chains of reasoning that allow us to explain why certain complicated phenomena happen in terms of simple rules the foundation that every single one of those chains rests on is "because the world is observed to work this way".

Both mass and force and acceleration are defined as independent measurable quantities. A balance measures mass, a spring scale measures force, and a meter stick and clock measure acceleration. Newton's Second Law relates the three quantities. This leaves open the distinction between inertial mass and gravitational mass, but separate experiments can show that they are numerically the same.

At heart, force is "amount of push", but how do you define this? You can't, without making some appeal to a deeper law. Your statement about inertial and gravitational mass belies this -- gravitational mass isn't a thing without a gravitational law. Show 3 more comments.

Active Oldest Votes. Suppose that you were to perform the following experiments: 1. Like this: b If you happen to find a ball that is moving with constant velocity, that is it moves in a straight line and it moves equal distances in equal times.

Like this: What we find is that if we are in a place where the ball is not interacting with anything air, gravity, etc. Now suppose that the ball is not moving and you shot this arrow to move it, you have the same conditions as before: As you can see the ball wasn't moving and now it is moving, so it accelerated. Improve this answer. M Katz 5 5 bronze badges. Keith Keith 6 6 silver badges 22 22 bronze badges. Add a comment. Descartes' laws are very similar to Newton's first law of motion.

Newton's second law says that when a constant force acts on a massive body, it causes it to accelerate, i. In the simplest case, a force applied to an object at rest causes it to accelerate in the direction of the force. However, if the object is already in motion, or if this situation is viewed from a moving inertial reference frame, that body might appear to speed up, slow down, or change direction depending on the direction of the force and the directions that the object and reference frame are moving relative to each other.

The bold letters F and a in the equation indicate that force and acceleration are vector quantities, which means they have both magnitude and direction. The force can be a single force or it can be the combination of more than one force.

It is rather difficult to imagine applying a constant force to a body for an indefinite length of time. In most cases, forces can only be applied for a limited time, producing what is called impulse.

For a massive body moving in an inertial reference frame without any other forces such as friction acting on it, a certain impulse will cause a certain change in its velocity.