Chapter 3: Forces
Date:____________
Section 1.2: Types of Friction - Notes
Learning Goals:
 Describe the four different types of friction.
 Observe the effects of air resistance on falling objects.
Friction:
 Friction: a force that _________________ motion between two surfaces that are touching each other.
o
Why does this happen?

_________________________ form when microscopic dips
and bumps that occur on a surface, no matter how smooth
it may seem, come into contact with another surface.

The greater the force pushing the two surfaces together,
the stronger the microwelds will be, which causes greater
friction. For an object to __________________, the force
must be strong enough to overcome the microwelds.
Types of Friction:
 There are 4 main types of friction:
o
o
o
o

______________________________: Occurs between two surfaces that are touching, but not moving
past each other.
o

The object will _______________________.
______________________________: Force that opposes the motion of two surfaces sliding past each
other.

______________________________: Friction between the rolling object and the surface it rolls on.

______________________________: Occurs when a solid object is in contact with a fluid (a gas or
liquid) and a force is applied to either the object or to the fluid
Coefficient of Friction:
 Number which represents the ____________________________ between two surfaces.
o
Ranges from _____________

The higher the coefficient, the _____________________________________ between the two surfaces

f=

o
f=
o
Fdrag = the force it takes to ______________________________ in its normal direction of travel
o
Fgravity = the _____________________ of the same object in the same units as the drag force
Practice:
o A book has a weight of 5 N. It takes 3 N of force to drag the book across the surface of a
sidewalk. What is the coefficient of friction?