can someone explain me why f=ma ?

vansh123

hey thanks guys for your help
i had solved so many questiond on newtons laws of motion but i didnt get the correct meaning of his second law

Jolb

I find it exceptionally beautiful that even the most basic laws of physics have such nuanced philosophical interpretations. The arguments presented here really show how hollow "definitions" can be, and how ambiguous "empirical laws" can be.

GarageDweller

Personally, I look at newtons laws as instructions for how to construct other equations based on observations.
The third law is just a statement of the conservation of momentum, nothing much to see there.
You have to take note that, although a law might be named after someone, the law that we write down nowadays can be drastically different from the one originall derived.
Originally, newton defined force as the rate of change of momentum.
This way he essentially described a model for how the universe could function.
Every particle has a momentum vector assigned to it (newton used the words motion and momentum interchangingly), it's time derivative is equal to the outside interactions which he calls force.
Position, velocity and acceleration can be defined from this.
To summarize, I see newtons first and second laws as describing the arena in which all of classical mechanics takes part in, given the initial conditions and outside forces, solve for the trajectory of the particle.

joeh1971

DaleSpam doesn't know what he is talking about. Newton's 2nd law is an empirical relation between force and acceleration, it is not a definition although some people do use it as an operational definition of mass. I can measure force and acceleration seperately and Newton's 2nd law tells me the mathematical connection between the two. Newton's 1st law is just a special case of Newton's 2nd law. Newton's 3rd law tell's us something about the forces that two objects exert on each other when they interact - that those forces are equal in magnitude and point in opposite directions.

harrylin

This was extensively discussed in earlier threads, such as:

http://www.physicsforums.com/showthread.php?t=529462

http://www.physicsforums.com/showthread.php?t=565187

BTW, it was found shortly before the introduction of relativity that "force=mass x acceleration" fails at very high speed; that expression is definitely empirical.

DaleSpam

Experimental prototypes of force are not nearly as reliable as measurements of acceleration or experimental prototypes of mass. So generally it is preferable to take Newton's 2nd as a definition of force, since you can get more accurate results that way than by using an experimental prototype force. Your rather rude assertions notwithstanding.

tkjtkj

it merely means that there is a relationship between the effect that the Higgs field has on a mass is directly proportional to a force applied to it and indirectly proportional to the accelleration the mass might experience due to a force, and that the 'constant of proportionality' is equal to " 1 "

Does this help? I'm curious as to what other replies you might have received ... Kindly let me know!

Andrew Mason

Newton observed, as did Galileo (which is why we refer to the principle as Galilean Relativity), that the laws of physics are the same in a boat moving at constant speed on calm seas as they are on land. In other words, the laws of motion are the same for bodies in all inertial reference frames (frames of reference of a body undergoing no change in motion).

If acceleration was not proportional to force (and inversely proportional to mass) two very important principles would be violated: 1. the additive nature of forces and mass and 2. Galilean relativity.

AM