Force: Newton's First and Second Laws

Newton's Laws describe the action of objects in response to forces.
(Digression) The response of an object to a given force is a measure of its inertial mass ... which turns out to be equivalent to its gravitational mass.
Newton's Second Law states
```
          Force = mass * acceleration
```

This shows that the units of force must be

                              kg * m
          (kg) * (m/s^2) =   --------      (Newtons)
                                s^2

Note that if the net force on a body is zero, then its acceleration must also be zero -- this is Newton's First Law.
Here on earth, friction exerts a force on just about all objects, so they are always accelerating; that's what makes it hard to realize that the natural state of an object is to move with constant velocity (not be at rest).
In order to figure out which way an object moves in response to several forces, and how fast it accelerates, it helps to break up all forces into X and Y components, the add up the components.

Viewgraphs

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