# Newton's Laws by LisaB1982

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```									Chapter 3
Newton’s Law
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Newton’s Laws
Newton’s First Law Law of Inertia  Newton’s Second Law F = ma  Newton’s Third Law Action Reaction  Law of Universal Gravitation Gmm'


F

r

2

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Mass
 …is  …is

measured in kilograms. the measure of the inertia of an object.

 Inertia

is the natural tendency of a body resist changes in motion.

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Force
 …the

agency of change. velocity.

 …changes the

 …is

a vector quantity. Newton’s.

 ...measured in

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Newton’s First Law
 Law
 “A

of Inertia

body remains at rest or moves in a straight line at a constant speed unless acted upon by a force.”

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Newton’s First Law
mention of chemical composition  No mention of terrestrial or celestial realms  Force required when object changes motion  Acceleration is the observable consequence of forces acting
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 No

Newton’s Second Law
The Sum of the Forces acting on a body is proportional to the acceleration that the body experiences

F  a

 F = (mass) a
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  F  ma

Net Force

 Fx  max
 Fy  may

 Fz  maz
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Newton’s Third Law
 Action-Reaction

 For

every action force there is an equal and opposite reaction force

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The Law of Gravity
mass exerts a force of attraction on every other mass.  The math…
 Every

Gmm' F 2 r
G = 6.67  10-11 N·m2/kg2
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Gravity Questions
 Did

the Moon exert a gravitational force on the Apollo astronauts? kind of objects can exert a gravitational force on other objects?

 What

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Gravity Questions
 The

constant G is a rather small number. What kind of objects can exert strong gravitational forces? the distance between two objects in space is doubled, then what happens to the gravitational force between them?
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 If

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Weight
 The

weight of an object FW is the gravitational force acting downward on the object. mg

 FW =

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Tension
(Tensile Force)
 Tension

is the force in a string, chain or tendon that is applied tending to stretch it.

 FT

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Normal Force
 The

normal force on an object that is being supported by a surface is the component of the supporting force that is perpendicular to the surface.

 FN

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Coefficient of Friction
 Kinetic

Friction • Ff = mk FN Friction • Ff  ms FN most cases, mk < ms.
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 Static

 In

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On to problems...

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