4.2 Friction Flashcards
Friction🡪
the force that opposes motion
whenever one surface moves against another.
sliding friction
Makes it difficult to slide one surface past another.
rolling friction
Makes it difficult to roll one surface past another.
fluid friction
Makes it difficult to move an object in a fluid.
The amount of friction between two
substances depends on many factors:
The types of substances
Size and shape of the moving object
Temperature
Moisture content (wet vs. dry)
Static Friction 🡪
The force that prevents an object from starting to move.
true or false
static friction is related to static electricity
false
“Static” means
stationary
Kinetic Friction 🡪 It is always in the opposite
direction to the motion.
the force of friction that
opposes the movement of objects once they
are in motion.
Kinetic Friction is always in the _______________ to the motion.
opposite direction
Normal Force 🡪
force at 90o angle [up] from the
surface an object is on.
coefficient of friction
It is different for different substances and also
depends on if the object was moving (kinetic
friction) or not (static friction).
Coefficient of Kinetic Friction (μk) 🡪
relates the magnitudes (not directions) of the Force of Friction, Ff, the normal force, Fn, and the coefficient of kinetic friction.
Coefficient of Static Friction (μs) 🡪
relates the magnitudes of the maximum Force of Friction, Ff, just before the object MOVES, the normal force, Fn, and the coefficient of static friction.
helpful friction
Tires on snowy roads
Brakes in your car
Your own feet on the ground (without friction, you can’t move at all)
