Transcript There are 4 main types of friction

Chapter 12
Section 1
Forces
It was named after Sir Isaac Newton (the guy
under the apple tree) – who explained how
force, mass, and acceleration are related.
If the object is not moving, it will continue to not
move.
If the object IS moving, it will continue to move at the
same speed and in the same direction.
This acceleration can be a change in speed, in
direction, or both.
Without friction, everything would be slippery.
(even more slippery than a sheet of ice)
Note that “touching” each other includes solid
objects that are directly touching one another
as well as objects moving through a liquid or
gas.
There are 4 main types of friction:
static friction, sliding friction, rolling friction, and
fluid friction
* Always opposes your push
* Because sliding friction is less than static
friction, less force is needed to keep an object
moving than to start it moving
* Rolling friction is much less than static and
sliding friction – which is why wheels are so
useful for moving heavy objects.
NOTE: rolling friction does not actually exist – this
is one of those things textbook authors make up
in a misguided attempt to help you.
* Fluid friction increases as the speed of the
object moving through it increases. (So the
faster you stir, the greater the friction is.)
* Air resistance is fluid friction acting on an
object moving through the air. (So the faster
you drive, the more air resistance there is.)
We can decrease our terminal velocity
by increasing the (upward force of) air
resistance by increasing our surface
area.
• This is what a skydiver’s parachute does.
• Cats and flying squirrels spread all four
legs out to increase their surface area –
which increases their air resistance – to
decrease their terminal velocity.
(air resistance and gravity)