Calculations for Static and Kinetic Friction:

Ffr = µN

?is the coefficient of friction, this changes depending on the materials and the surfaces in contact. Static friction (µs) has a different coefficient then kinetic friction (µk) The amount of force needed to overcome an object's inertia is greater then the amount of force needed to keep it moving. This is due to the fact that,

in general,

µs >µk.