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Laws of Motion
Classical Mechanics
A brief overview
Aristotle (384 - 322 BC)
Natural Motion
All objects have internal
homing instincts similar
to those observed in
animals
Galileo (1564 - 1642)
Law of Falling Bodies
All bodies fall with a
constant acceleration
under gravity regardless
of mass
Kepler (1571 - 1630)
Laws of Planetary
Motion
Planetary orbits are
elliptical
Isaac Newton (1643 - 1727)
1661: Entered Trinity
College, Cambridge
1665: Received his
Bachelor’s Degree.
University closed due to
Plague. Re-opened 1667.
1668: Awarded Masters
degree
Law of Universal Gravitation
W=mxg
• W = weight (N)
• m = mass (kg)
• g = acceleration due to gravity (m/s2 )
Acceleration due to gravity of falling body on Earth
(excluding effects of air resistance) is, on average,
9.8 m/s2
This value is often rounded off to 10 m/s2
Principia (1669)
1669 - 1687
Lucasian Professor of
Mathematics
(Cambridge)
Newton’s Scientific
Achievements
• Law of Universal Gravitation
• Laws of Motion
• Advances in Optics - studies of colour &
light
• Constructed the first reflecting telescope in
1668
• Calculus
Newton’s
st
1
Law
• An object that is at rest will stay at rest
until an unbalanced force acts upon it.
• An object that is in motion will not change
its velocity until an unbalanced force acts
upon it.
Newton’s
nd
2
Law
• A body will accelerate with acceleration
proportional to the force and inversely
proportional to the mass
F=mxa
• F = Net Force (N)
• m = mass (kg)
• a = acceleration (m/s2 )
Momentum
p=mxv
• p = momentum (kg.m/s) or (N.s)
• m = mass (kg)
• v = velocity (m/s)
Momentum
• Can be defined mathematically.
• Is a vector because it has magnitude as well
as direction.
• When bodies collide, momentum is
transferred.
• In any collision, momentum is conserved.
Law of Conservation of
Momentum
The total momentum of a system is the same
before a collision as after.
m1u1 + m2u2 = m1v1 + m2v2
Impulse
• Is defined as the change in momentum
experienced by a body.
Δp
= m x Δv
Δp = F x Δt
Newton’s
rd
3
Law
• Every action has a reaction equal in
magnitude and opposite in direction
Newton’s 3rd Modelled
Some weblinks ….
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Crash Test Results
http://www.youtube.com/watch?v=zmUBgTHppv8
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NASA movie ‘Orville and Wilbur Wright’ Newton’s Laws and Flight
http://www.grc.nasa.gov/WWW/K-12/airplane/newton.html
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Space Shuttle launches
http://www.youtube.com/watch?v=4FROxZ5i67k
http://www.youtube.com/watch?v=iwfsFtpACFw&feature=related
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NASA Apollo 11 Mission
http://www.youtube.com/watch?v=LNm1LVJTJ2k&feature=related
http://www.youtube.com/watch?v=wdSPF7ujsdw&feature=related
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NASA TV
http://www.youtube.com/NASATelevision