Newton’s First and Second Newton’s First and Second Laws of MotionLaws of Motion

12.212.2

I. ScientistsI. ScientistsAristotle, Galileo and Newton all worked Aristotle, Galileo and Newton all worked

on concepts of force and motionon concepts of force and motionAristotle- incorrectly proposed that force is Aristotle- incorrectly proposed that force is

required to keep an object moving at required to keep an object moving at constant speed, this error held back constant speed, this error held back progress in the study of motion for almost progress in the study of motion for almost two thousand years. two thousand years.

Galileo- helped correct misconceptions Galileo- helped correct misconceptions about force and motionabout force and motionConcluded that moving objects not subjected Concluded that moving objects not subjected

to friction or any other force would continue to to friction or any other force would continue to move indefinitely move indefinitely

Newton- built on the work of Galileo and Newton- built on the work of Galileo and defined force and mass. He introduced his defined force and mass. He introduced his laws of motion in laws of motion in Principia-Principia- his book his book

II. Newton’s First LawII. Newton’s First LawThe state of motion of an object does not The state of motion of an object does not

change as long as the net force acting on change as long as the net force acting on the object is zero the object is zero

An object at rest remains at rest unless an An object at rest remains at rest unless an unblanced force acts on itunblanced force acts on itex: kicking a soccer ballex: kicking a soccer ball

InertiaInertia- the tendency of an object to resist - the tendency of an object to resist a change in motion a change in motion

Upon impact, the test dummy continues forward until it hits something – inertia

III. Newton’s Second LawIII. Newton’s Second Lawacceleration = acceleration = net forcenet force = = FF mass m mass m

The acceleration of an object is equal to The acceleration of an object is equal to the net force acting on it divided by the the net force acting on it divided by the object’s massobject’s massEx: the more force you apply to throwing a Ex: the more force you apply to throwing a

ball the more the ball accelerates ball the more the ball accelerates This law also works on forces in opposite This law also works on forces in opposite

directions directions Ex: seatbelts in cars- explain Ex: seatbelts in cars- explain pg 367 Math Practice #1-3 pg 367 Math Practice #1-3

IV. Weight and MassIV. Weight and MassWeight- the force of gravity acting on an Weight- the force of gravity acting on an

objectobjectWeight = mass x acceleration due to gravity Weight = mass x acceleration due to gravity

(9.8m/s (9.8m/s22)) mass is a measure of the inertia of an mass is a measure of the inertia of an

object; weight is a measure of the force of object; weight is a measure of the force of gravity acting on an object gravity acting on an object

PlanetPlanet Multiply your Multiply your weight by:weight by:

New weightNew weight

MercuryMercury 0.40.4

VenusVenus 0.90.9

EarthEarth 11

MarsMars 0.170.17

JupiterJupiter 2.52.5

SaturnSaturn 1.11.1

UranusUranus 0.80.8

NeptuneNeptune 1.21.2

MoonMoon 0.170.17