Static Friction fs = UsFn Kinetic
Friction
fk
=
UkFn
(force to start object moving)
Horizontal
surface
fs = Us w fk
= Uk w AND w = mg
Ex
1) A 1000 N
car skids on a wet concrete road. If the road is horizontal, what is the
friction force on the car?
Ex
2) A skier
is being pulled along a horizontal surface at constant speed with a
force of 50 N. What is the weight of the skier?
Ex
3) A 10 kg
block of wood sliding on a horizontal wooden table is brought to rest. What is
the force on the block of wood that caused it to stop?
Ex 4) A 53 kg piece of copper is at rest on a horizontal steel table. A force is
applied to the box and it achieves an acceleration of 0.1 m/s2. What
is the weight of the piece of copper?