Unit 2: Part 1- Newton's Laws

AP Physics C: Newtons Laws

Force

Force

• push or pull on an object

• vector quantity

• forces arise from interactions

• Units: N, lbs

newtons

kgm/s²

pounds (lbs)

slugsft/s²

Equilibrium

• net force on a body of zero

Object in equilibrium

• could have constant velocity

• at rest

contact force

involve contact between objects (normal, friction, tension)

field forces

act without necessity of contact (gravity, electromagnetic, strong, weak)

gravity force

Fg, mg

friction

• F/k

• F/s

• fs

• fk

normal

• F_n

• N

tension

• F_T

• T

drag

F_D

newton’s first law

a body at rest will remain at rest and a body in motion will continue with a constant velocity unless acted upon by an unbalanced force.

newton’s second law

a body acted upon by a net external force will accelerate. the acceleration is directly proportional to the net force and inversely proportional to the mass. it is in the direction of the net force.

newton’s third law

• if A exerts a force, F on B, then B exerts a force of -F on A

• these forces occur simultaneously, are of the same type, and make an “interaction pair”

• the forces in an interaction pair act on different objects and DO NOT CANCEL OUT

inertia

tendency of objects to resist a change in motion

mass

• same as inertia (to physisist)

• the same everywhere

• units: kg, slugs

weight

• gravitational attraction (force)

• changes depending on location

weight equations

• W = mg

• Fg = mg

normal force

• the force that keeps one object from invading another object

• “normal” = “perpendicular”

• must take gravitational force into account

• scale reading, apparent weight

tension

• a pulling force

  • generally exists in a rope, string, or cord

  • massless or very light strong

  • same throughout

  • arises at the molecular level with a rope, string, or cable resists being pulled apart