# How do simple machines change the direction of force?

Jul 8, 2018

Simple machines use a pivot point to modify the magnitude and/or direction of a force.

#### Explanation:

Forces are vector quantities so they combine as vectors.

Simple machines use a pivot point such as a lever fulcrum or axle bearing to provide a "counteractive" force to combine with the applied force(s) to produce a resultant force, acting in a different direction and/or with a different magnitude to that applied.

The forces must comply with the rules of Newtonian physics,

$F = m a$
i.e. if the forces are not in balance then something will be accelerating.

$W = F \cdot d$
work = force * distance (= energy)

$p o w e r = \text{energy / time}$, etc.

For a lever in balance ${F}_{1} \cdot {L}_{1} = {F}_{2} \cdot {L}_{2}$ :

Note that there must be a counteractive force acting upwards at the fulcrum if the lever is in balance Gears, wheels and pulleys use the same principles but allow continuous movement, whereas a lever has a limited range of movement.