1. Physics is a drag!

2.  The force that resist motion  Ff  Measured in Newtons  Acts parallel to the surface in contact  Acts opposite to the direction of motion

3.  Depends on the nature of the materials in contact.  Independent of speed or area of contact.  Proportional to the force pressing the surfaces together (same as F N )  2 kinds  Static (stationary-force you must overcome to start moving)  Kinetic (between surfaces that are moving)

4.  Symbol : µ  A value that represent the amount of friction between 2 surfaces (no units)  Calculated by taking F f /F N  µ s : coefficient of static friction  µ k : coefficient of kinetic friction  To find Ff simply multiply µ by F N

5. Fg FNFN FaFa FfFf F f = µF N F N = Fg but why? But how do you find Fg? Fg = mg =m(9.80m/s 2 )