contact force: a force that acts between two objects when they touch each other

non-contact force: a force that acts between two objects without the objects touching; also called action at a distance force

common forces

$\overrightarrow{F_g}$= force of attraction between all objects due to mass

$\overrightarrow{F_t}$= force exerted by objects that can be stretched

$\overrightarrow{F_{air}}$= the friction between objects and the air around them

$\overrightarrow{F_n}$= a force perpendicular to the surface between objects in contact

$\overrightarrow{F_f}$= a force that opposes the sliding of two surfaces across one another, acts opposite to motion or attempted motion

$\overrightarrow{F_s}$= a force that resists attempted motion between two surfaces in contact

$\overrightarrow{F_k}$= a force exerted on a moving object by a surface in the direction of motion opposite to the motion of the object

$\overrightarrow{F_a}$= a force due to one object pushing or pulling on another

net force ($\Sigma\overrightarrow{F}$) = the sum of all the forces acting on an object

free body diagram: a simple line drawing that shows all the forces acting on an object

Rules for components:

• pay attention to positive vs negative direction
• create the net X and net Y equations as a summation of the horizontal and vertical forces
  • express $\Sigma{F}$ with respect to all forces by using pythagorean theorem
  • to determine the angle measure, use $\tan\theta = \frac{\Sigma{F_y}}{\Sigma{F_x}}$
• to figure out the final direction, take the signs of the x and y componets