a body in a free fall falls down with gravity (g) and its mass (m), so the law is F=mg,why it is not F=m+g?
final velocity is equal to the square root of twice the acceleration times the distance.
9th grade physics you can also cancel out the metrics to yield final velocity parameter.
because when you write F=m+g , its addition, where as F= mg means 'm xg' where its multiplication , so here force = mass multiplied with gravity .
Answers:
F=ma (or in this case, since a=g, F=mg), is Newton's 2nd law of motion. Newton's second law of motion explains how an object will change velocity if it is pushed or pulled upon.
This law, or 'rule of thumb' has been experimentally verified over and over and over. It is not exactly true, especially in extreme circumstances, but it is very close to correct. We use it because in most situations, it works very well and we can experimentally verify it. We can make predictions based on it which come true, so it is useful.
First of all, you can not add up quanities of different units, i.e. M is in Kilograms and G is meters per sec aquared. So M+G would be total nonsense. You can only add/subtract quanities of identical measure, like adding 2 kilogram to 3 kilgram and get 5 kilogram, or add 2 meters per sec per sec acceleration to 3 meter per sec per sec acceleration to get 5 meter per sec per sec. But this is not why F=mg. This just explains why F is NOT m+g.
The above is a technical reason why F is not = mg. If your question is more along the line of: why is the force on a mass depends on its mass m and its acceleration a, but not on something else? That is more of a philosophical question, to which we still don't have an answer to.
