Newton's Laws of Motion

Every object continues in a state of rest or of uniform speed in a straight line unless acted on by a nonzero (unbalanced) force.
Inertia is an object's resistance to change in its state of motion.
A change in velocity requires an unbalanced (net) force.

The acceleration produced by a net force on an object is:
- Directly proportional to the net force ( $F_{net}$ ).
- In the same direction as the net force.
- Inversely proportional to the mass ( $m$ ) of the object.
Equation: a=Fnet/ma=m or Fnet=ma
Where a is acceleration

Unit of force: Newton ( $N$ ) = $kg \cdot m/s^2$
Free Fall:
- Occurs when gravity is the only force acting on a falling object (negligible air resistance).
- Acceleration is constant, approximately $g = 9.8 \ m/s^2$ (often rounded to $10 \ m/s^2$ ).
- All objects, regardless of mass, fall at the same acceleration in free fall because the ratio of weight ( $w$ ) to mass ( $m$ ) is constant ( $g = w/m$ ) in a given location.
Non-Free Fall:
- Occurs when other forces, like air resistance, act on a falling object in addition to gravity.
- Acceleration is less than $g$ .
- As an object's speed increases, air resistance increases.
- Terminal Velocity: Achieved when the force of air resistance equals the object's weight, resulting in zero net force and zero acceleration; the object falls at a constant velocity.

Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.
Action and reaction forces:
- Are co-pairs of a single interaction.
- Are equal in strength and opposite in direction.
- Always act on different objects.
- Example: Object A exerts force on B (action), Object B exerts force on A (reaction).
When forces are applied to objects of different masses ( $F=ma$ ), they will experience different accelerations.