# Question #6f4b2

Oct 6, 2015

I would say through Newton's Second law:
$\Sigma \vec{F} = m \cdot \vec{a}$

#### Explanation:

From this fundamental law you can see that forces (or resultant of) are connected directly to acceleration that is the cinematic representative of motion. It represents a bridge between the cinematic effect of motion (=change of position in time) and the dynamic causes of (varied) motion (=forces).

Gravity is the general term used to indicate gravitational force of attraction between bodies with mass (on Earth we indicate it simply as Weight, another force, that is directly related, through again Newton's Law, to acceleration of gravity $g$ as: $W = m g$).

Friction is a force (even if a little bit weird) and is related to the Normal reaction that, in turn, is related to Weight.

Hope it helps!