Force and Friction Flashcards
A force that opposes motion between two surfaces that are in contact
friction
A push or pull exerted on an object
force
An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
Newton’s First Law
Net Force equals mass x acceleration (EF=ma)
Newton’s Second Law
For every action there is an equal and opposite reaction
Newton’s Third Law
a state in which opposing forces or influences are balanced.
equilibrium
Force is ________ not possessed (things don’t have force).
applied
Force and acceleration are ________ proportional
directly
Mass and acceleration are _________ proportional
inversely
Force due to gravity acting on mass (measured in pounds or newtons)
Weight
Force or gravity of the weight (newtons)
F (g) or W
acceleration due to gravity
a (g) or G
w = mg OR f = m a(g)
Finding weight
sum of all forces
net force
Kinetic (sliding), Static (at rest), Rolling (resistance to an object rolling), Fluid (between molecules of liquid or gas)
types of friction
Microscopic roughness, molecular attraction,
Causes of friction
The velocity where the force of air resistance up equals the weight down. Caused by the flow of air molecules past the surface (ex. skydiving)
Terminal velocity
Friction depends on…
Shape? NO
Mass? YES
surface area (ONLY for rolling and fluid, NOT for static and kinetic)
Velocity (Fluid YES, NO for others once object is in motion)
Texture? YES
the ratio of the friction to the normal force acting between two objects (measure of “stickiness” of materials in contact)
coefficient of friction
Ff/Fn = μ
coefficient of friction equation
If a = 0, then
Ff = Fa
Fn = Fg
Static friction is ________ than kinetic friction
greater
EF = Ff
ma = μFn
ma = μmg
a = μg
EF = ma
Fn = Fg
Equations for acceleration caused by friction
