Physics Test: Forces and Friction

Vectors

have magnitude and direction; represented as arrows

Equilibrium

a condition in which the object is not moving or is moving at a constant velocity. Fnet x and Fnet y both = 0

Equilibriant

one single force that when added to the object will put the object in equilibrium, resultant of all vectors, same magnitude but opposite direction

Tension

forced caused by ropes or chains

Determining Fn

Fnet y = Fw + Fn = 0. Fw = mg

What is inertia and what does it depend on?

NOT a force, depends on mass only, it is a resistance to a change in motion

Fnet

net force, Fnet x = FF + FA = ma, Fnet y = Fn + Fw = 0; slope of a velocity/time graph x mass

Newtons First Law

describes motion, forces on one object, balanced forces so Fnet = 0, object stays at rest or moves at a constant velocity

Newtons Second Law

describes motion, forces on one object, object will accelerate if there is a net force acting on the object; Fnet = ma

Newtons Third Law

does not describe motion, deals with more than one object, forces between two objects are equal and opposite

Mass

the amount of matter in an object, would not change in space, base unit is kg

Weight

gravitational force on an object, changes by location, unit is N

Static Friction

not moving but a force is applied, FFs, Mu(s) = the absolute value of FFs/Fn

Kinetic Friction

sliding friction, FFk, Mu(k) = the absolute value of FFk/Fn

Mu

absolute value of FF/Fn, only depends on the tyoes of surfaces in contact, no units

Four Corners of the Puzzle

1. Force Diagram

2. Break vectors into components if at an angle

3. Find Fnet x and Fnet y

4. Mu = FF/Fn

5. Use big 3 equations if needed

Big 3 Formulas

Vf = Vi + at; Vf² = Vi² + 2ax; x = Vit + ½at²

Other Formulas

Fnet = ma; Fw = mg; Mu = FF/Fn