# Physics [[Kinematics & Dynamics]] is the study of motion. It describes the way objects move, including their velocity and acceleration. **Dynamics** is the study of how forces affect the motion of objects and systems. It considers the causes of motion of objects and systems of interest. ## Mass & Weight Mass is the measure of how muchh matter an object contains. - It is consistent for an object regardless of gravity > **Mass** > - The measure of how much matter an object contains > - Is consistent for an object regardless of gravity > **Weight** > - The force exerted on a mass by gravity > - Not a constant, changes based on local gravity ## Newton's Laws of Motion ### First Law > [!summary] **Newton’s First Law** > A body at rest **remains** at rest or, if in motion, remains in motion at a constant velocity unless acted on by a net external force. ^Newtons-First-Law #### Gravitation and Inertia Both gravitation and inertia are connected to mass ### Second Law > [!summary] **Newton’s Second Law** > The acceleration of a system is directly proportional to and in the same direction as the net external force acting on the system and is inversely proportional to its mass: > > $\vec{a} = \frac{\vec{F_\text{net}}}{m}$ > ^Newtons-Second-Law ### Third Law > [!summary] **Newton’s Third Law** > A body at rest **remains** at rest or, if in ^Newtons-First-Law