LECTURE #3 - force of friction Flashcards
what is friction (mechanical behaviour of objects in contact) ?
- force acting at interface of surfaces in contact
- acts in a direction parallel to the area of contact
- opposes the tendency to more
what is friction working against ?
action force
what does F(subscript A) =
action force
what does R(subscript N) =
Normal reaction force
what does F(subscript s) =
static friction force
what does F(subscript k) =
kinetic friction force
what does static mean ?
not moving
what does kinetic mean ?
,loving
what does F(subscript m) = ?
max static friction
what happens once static friction threshold is reached ?
it drops and starts
TRUE OR FALSE ?
friction is at a steady kinetic level
TRUE
what two things does friction force depend on ?
normal reaction force and coefficient of friction
what is normal force ?
force acting perpendicular to surface of object
what is tangential force ?
force acting parallel to surface object
what is coefficient of friction ?
indicated relative ease of sliding between two surfaces in contact (not describing a single surface)
what are some factors of friction ?
- roughness & hardness of surfaces
- type of molecular interaction of surfaces
TRUE OR FALSE
static and kinetic values differ ?
TRUE
what is kinetic friction ?
friction force generated between two surfaces in contact
TRUE OR FALSE
remains constant F(subscript k) < F(subscript m)
TRUE
FILL IN THE BLANK
friction force ________ depend on the surface area (contact area)
does not
TRUE OR FALSE
typically, wider objects have greater weight
TRUE
is it easier to pull or push?
pull
when you pull you usually have an upward component of force so …
(increased of decreased)
the normal force is ___________ and therefore the friction force is _________
decreased
when you push you usually have an downwards component of force so …
(increased of decreased)
the normal force is ___________ and therefore the friction fore is _________
increased
is normal force parallel or perpendicular ?
perpendicular
TRUE OR FALSE
applied force must exceed friction
TRUE
TRUE OR FALSE
gravity pulls object down
TRUE
