Newtons Laws Opt
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Transcript of Newtons Laws Opt
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Chapter 3Chapter 3
Newton’s LawNewton’s Law
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Newton’s Laws Newton’s Laws
3 Newton’s First Law
xLaw of Inertia
3 Newton’s Second Law
xF = ma
3 Newton’s Third Law
xAction Reaction
3 Law of Universal
Gravitation
2
'
r
Gmm F =
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MassMass3 …is measured in kilograms.
3 …is the measure of the inertia of an object.
3 Inertia is the natural tendency of a body resist
changes in motion.
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ForceForce3 …the agency of change.
3 …changes the velocity.
3 …is a vector quantity.
3 ...measured in Newton’s.
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Newton’s First LawNewton’s First Law3 Law of Inertia
3
“A body remains at restor moves in a straight
line at a constant speed
unless acted upon by a
force.”
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Newton’s First Law
3No mention of chemical composition
3No mention of terrestrial or celestial
realms3Force required when object changes
motion
3 Acceleration is the observableconsequence of forces acting
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Newton’s Second LawNewton’s Second Law
The Sum of the Forces acting
on a body is proportional to
the acceleration that the body
experiences
ΣF ∝ a
Σ F = (mass) a
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am F
=
x xma F =∑
y y ma F =∑
Net Force
z z ma F =∑
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Newton’s Third LawNewton’s Third Law3 Action-Reaction
3
For every action forcethere is an equal and
opposite reaction force
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The Law of GravityThe Law of Gravity3 Every mass exerts a force of attraction on
every other mass.
3 The math…
2
'
r
Gmm F =
3G = 6.67 × 10-11 N·m2/kg2
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Gravity QuestionsGravity Questions3 Did the Moon exert a gravitational force on
the Apollo astronauts?
3 What kind of objects can exert a
gravitational force on other objects?
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Gravity QuestionsGravity Questions
3 The constant G is a rather small number.
What kind of objects can exert strong
gravitational forces?
3 If the distance between two objects in space
is doubled, then what happens to thegravitational force between them?
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WeightWeight
3 The weight of an object FW is the
gravitational force acting downward on the
object.
3 FW = m g
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TensionTension(Tensile Force)(Tensile Force)
3 Tension is the force in a string, chain or
tendon that is applied tending to stretch it.
3 FT
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Normal ForceNormal Force
3 The normal force on an object that is being
supported by a surface is the component of
the supporting force that is perpendicular tothe surface.
3 F N
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Coefficient of FrictionCoefficient of Friction
Kinetic Friction
• Ff = µk F N
3 Static Friction
• Ff ≤ µs F N
3 In most cases, µk < µs.
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