4.3 Friction Flashcards
What is friction?
the resistance that one surface or object encounters when moving over another.
What are the two categories of friction?
static friction
kinetic friction
What is static friction?
no relative motion between the surfaces that are in contact
What is kinetic friction?
sliding friction; when there is relative motion between the two surfaces that are in contact
What is the normal force?
perpendicular component of the contact force exerted by a surface on an object
What does normal mean?
perpendicular
What is the normal force equal to for an object on a horizontal surface with no other vertical forces?
the weight of the object
In the case of kinetic friction, what is the magnitude of the force of friction equal to?
magnitude of the force of friction is proportional to the magnitude of the of the normal force
What is mu(k)?
coefficient of kinetic friction
What is the equation for the force of kinetic friction?
Ff = mu(k)F(normal)
What is the direction of the force of kinetic friction?
parallel to the surface and in the opposite direction to the objects velocity
What is mu(s)?
coefficient of static friction
What is the equation for maximum force of static friction?
Ff = (mu)sF(normal)
Which is always greater; mu(s) or mu(k)?
mu(s)
