Newton’s First Law of Motion - Inertia Chapter 4 Newton’s First Law of Motion - Inertia

Things want to be at rest Natural Motions: Aristotle Things want to be at rest Natural Motions: heavy things go down light things go up stars make circles planets are ‘wanderers’

Photographic evidence of stars moving in circles

Aristotle II Violent Motions: Motion caused by something Sail pushes boat Bow shoots arrow

Galileo Force: a push or pull Friction: force that acts between materials that touch caused by surface irregularities

Galileo Only when friction is present is force needed to keep an object moving

Objects want to be at a constant velocity: Newton Objects want to be at a constant velocity: “Objects at rest tend to stay at rest” - velocity of zero

Do you believe Newton? “Objects at rest tend to stay at rest” Tests?

Newton “Objects in motion, tend to stay in motion” Objects will move in the same direction and same velocity with out gravity, friction, or air resistance

Newton’s First law of Motion (Law of Inertia) Objects tend to stay at a constant velocity.

Mass A measurement of the amount of matter (stuff) in an object Units: Grams/kilogram

Amount of force that gravity places on an object Weight Amount of force that gravity places on an object Units: Newton 1 kg = 9.8 N

Calculating Weight Weight = gravity * mass 9.8(m/s2)*1(kg) = 9.8(N)

Comparing Mass vs. Weight vs. Volume Same mass -> same place -> same weight Same volume -> same material -> same mass

Subtract opposite forces Add forces in same direction Net Forces: Vectors! Subtract opposite forces Add forces in same direction Force remaining is net force

Equilibrium Forces all cancel - 0 net force

The air is moving with the earth! The earth is moving! Bird and worm Jumping in the air Coin in a car/plane The air is moving with the earth!