pysics - Newtons Laws

Friction

Force that opposes motion between two surfaces in contact

Coefficient of Friction (μ)

Constant that describes the "strength" of friction between surfaces

Static Friction

Friction that prevents an object from starting to move

Maximum Static Friction

Ff ≤ μs F_N

Kinetic Friction

Friction acting on an object while it is moving

Kinetic Friction Formula

Ff = μk F_N

Normal Force (Fₙ)

Force perpendicular to a surface

Inclined Plane

A slanted surface where forces are split into parallel and perpendicular components

Parallel Force on Incline

F_∥ = mg sin θ

Perpendicular Force on Incline

F_⊥ = mg cos θ

Net Force (Parallel)

Fnet = mg sin θ − Ff

Net Force (Perpendicular)

Fnet = FN − mg cos θ

Atwood Machine

Two masses connected by a string over a pulley

Inclined Atwood (m₁ up)

Fnet = FT − F_∥

Inclined Atwood (m₂ down)

Fnet = Fg − F_T

Newton's First Law (Law of Inertia)

An object at rest stays at rest and an object in motion stays in motion unless acted on by an unbalanced force

Inertia

Resistance to changes in motion

Mass

Amount of matter in an object; source of inertia

Weight

Force of gravity acting on an object

Gravity (F_g)

Weight force equal to mg

Force

A push or pull on an object

Equilibrium

No unbalanced forces acting on an object

Static Equilibrium

Object at rest

Dynamic Equilibrium

Object moving at constant velocity

Tension (F_T)

Pulling force transmitted by a rope, string, or cable

Applied Force (F_A)

A general push or pull applied to an object

Free Body Diagram

Diagram showing all forces acting on an object

Newton's Second Law

Acceleration is proportional to net force and inversely proportional to mass

Force Equation

F = ma

Net Force (x-direction)

ΣFx = max

Net Force (y-direction)

ΣFy = may

Acceleration Due to Gravity

9.8 m/s²

Pulley

Massless, frictionless device that changes direction of tension

Tension in Pulley Systems

Same throughout the rope

Heavy Mass Equation (Atwood)

m₁g − F_T = m₁a

Light Mass Equation (Atwood)

F_T − m₂g = m₂a

Modified Atwood Machine

Atwood system involving an inclined plane