Friction & Forces Concepts - PREP FOR PHYSICS UPCOMING TESTS

Newton's First Law of Motion

An object at rest stays at rest, and an object in motion stays in motion at constant velocity unless acted upon by a net external force.

Newton's Second Law of Motion

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass; mathematically expressed as ∑F = ma.

Newton's Third Law of Motion

For every action, there is an equal and opposite reaction.

Free-body Diagram (FBD)

A graphical illustration used to visualize the forces acting on an object.

Static Friction

The force that resists the initiation of sliding motion between two surfaces in contact; Ffs ≤ μs * FN.

Kinetic Friction

The force that opposes the motion of two surfaces sliding past each other; Ffk = μk * FN.

Weight (Fg)

The force exerted by gravity on an object, calculated as Fg = mg, where g is the acceleration due to gravity (9.8 m/s²).

Coefficient of friction (μ)

A numerical value representing the frictional properties between two surfaces; μs for static friction, μk for kinetic friction.

Projectile motion

The motion of an object thrown into the air with an initial velocity, subject to only the force of gravity.

Vertical projectile motion

Motion under the influence of gravity in the vertical direction, where acceleration is ay = -g = -9.8 m/s².

Horizontal projectile motion

Motion in which an object moves with constant horizontal velocity, ax = 0 m/s².

Angle of launch (Θ)

The angle at which an object is projected relative to the horizontal plane.

Initial velocity components

For an angled launch, the initial velocity is divided into horizontal (vix = vi * cos(Θ)) and vertical (viy = vi * sin(Θ)) components.

Equilibrium

A state in which the net force on an object is zero, resulting in no acceleration.

Acceleration

The rate of change of velocity of an object; occurs when there is a net force acting on the object.

Sum of Forces (∑F)

The vector sum of all forces acting on an object; used in Newton's second law as ∑F = ma.

Inclined Plane

A flat surface tilted at an angle, used to analyze forces acting on objects moving up or down the plane.