### Statement of Newton's Laws

*Question:* If an object is at rest, how can it start moving?

*Answer:* Apply a force.

*Question:* What do we need to do to keep a moving object moving?

*Answer:* Nothing! If no forces, the speed of an object does not
change!

**Newton's First Law:**
For no net force, an object at rest remains at rest, and an object moving at
constant velocity continues at constant velocity.

The *acceleration a,* the rate of change of the velocity,
is connected to the total force by:

**Newton's Second
Law: ** Σ**F** = m **a,**

where m is the mass of the object. Acceleration equals the total
force divided by the mass!

Note: Newton's laws apply in stationary or
constant-velocity reference frames---**inertial** frames. In non-inertial
(accelerating) frames, corrections to Newton's Laws arise because of the
acceleration.