Sir Isaac NewtonSir Isaac Newton

English physicist English physicist & mathematician& mathematician

……he developed he developed the 3 laws of the 3 laws of

motionmotionMotion is any Motion is any change in change in position!position!

p. 45p. 45Click here

ForcesForces

ForcesForces can have the ability can have the ability to to change motionchange motion!!!!!!

aa push or a push or a pullpull

Unit:Unit: Newton (N) Newton (N)

p. 46p. 46

ForceForce

Amount of matter Amount of matter (resists forces)(resists forces)

p. 47

vs.vs.

MassMass

Newton’s 1st LawNewton’s 1st Law (Law of (Law of Inertia)Inertia)““An object in motion wants to An object in motion wants to

stay in motion, an object at stay in motion, an object at rest wants to stay at rest.”rest wants to stay at rest.”

FYI- Inertia depends upon

mass.

Sir Isaac Newton’s Sir Isaac Newton’s 3 Laws of Motion:3 Laws of Motion:

p. 48p. 48

““Acceleration occurs in the Acceleration occurs in the direction direction of the force.”of the force.”

the object’sthe object’s mass…mass… and also theand also the

size of the size of the force…force… determine determine

the object’s the object’s accelerationacceleration

Newton’s 2nd Newton’s 2nd LawLaw (Law of (Law of

Acceleration)Acceleration)

p. 49p. 49

Formula:Formula: -

AcceleratioAcceleration n (m/s(m/s22))

Force Force (N)(N)

Mass Mass (Kg)(Kg)

Ex.) p. 49, 50Ex.) p. 49, 50

Newton’s 2nd Newton’s 2nd LawLaw (calculating (calculating

acceleration)acceleration)

p. 49p. 49

AA==FF//

mm

Types of ForcesTypes of ForcesForces cause Forces cause motionmotionMotion depends on net Motion depends on net forceforce

p. 51p. 51

Forces can beForces can be balancedbalanced oror unbalancedunbalanced

Balanced ForcesBalanced Forces

Like a tie in an Like a tie in an arm wrestling arm wrestling match!match!

Equal in sizeEqual in sizeOpposite in Opposite in directiondirectionNo motionNo motion occurs! occurs! (equilibrium(equilibrium))

p. 51p. 51

Unbalanced ForcesUnbalanced Forces

Opposite in direction2nd law2nd law: unbalanced forces cause acceleration

Unequal in size

p. 51p. 51

Gravity pulls Gravity pulls everything down with everything down with

a force of a force of 9.8 N9.8 N (Newtons)(Newtons)

GravityGravity

p. 52p. 52

A force that pulls us downwarddownward toward the center of the Earth.

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The gravitational force The gravitational force felt by an object is felt by an object is related related

to its massto its mass. .

MassMass does does NOT changeNOT change, , but your weight but your weight will will

change with a change in change with a change in gravity (moon)!gravity (moon)!

mass x gravity mass x gravity (force)(force)

MassMassAmount of matter Amount of matter

(resists forces)(resists forces)

p. 53

vs.vs.

WeightWeight

Formula:Formula: -

FFww==mmggWeight Weight force force

(N)(N)

Mass Mass (Kg)(Kg)

Gravity Gravity (9.8 m/s(9.8 m/s22))

p. 53p. 53

Calculating WeightCalculating Weight

FrictionFriction opposesopposes an object’s an object’s motionmotion

1. Air friction2. Viscous friction 3. Sliding friction4. Rolling friction p. 54

Four Types of Friction:Four Types of Friction:

Also calledAlso called Air resistanceAir resistance (aerodynamics reduce (aerodynamics reduce

the air friction the air friction))

1. Air Friction1. Air Friction

Ex) falling objects or airplanes

p. 54p. 54

Moving Moving through a through a liquid, or fluidliquid, or fluid

2. Viscous Friction2. Viscous Friction

Ex) swimming

p. 54p. 54

3. Sliding Friction3. Sliding FrictionTwo surfaces rub Two surfaces rub

against one against one anotheranotherEx) rubbing

hands or clapping

Caused by irregularities in Caused by irregularities in the surfacethe surface

p. 54

An object An object rolls rolls over a over a surfacesurface

4. Rolling Friction4. Rolling Friction

Ex) ball bearings, roller skates, or

wheels

p. 54Figure 3.9

““For every For every actionaction, , there is an equal and there is an equal and

opposite opposite reactionreaction.”.”

Newton’s 3rd Newton’s 3rd LawLaw

(Action /Reaction)(Action /Reaction)

p. 57p. 57

Formula:Formula:

PP==mmvvMomentum Momentum

(Kg-m/s)(Kg-m/s)

Mass Mass (Kg)(Kg)

Velocity Velocity (m/s)(m/s)

p. 58

Calculating Calculating MomentumMomentum

Total amount of Total amount of momentum can not changemomentum can not change

Law of Conservation of Law of Conservation of MomentumMomentum

p. 58p. 58ex.) p. 59ex.) p. 59