Laws of MotionClassical 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 PlanetaryMotion
Planetary orbits are
elliptical
Isaac Newton (1643 - 1727)
1661: Entered TrinityCollege, Cambridge1665: Received hisBachelor’s Degree.University closed due to
Plague. Re-opened 1667.
1668: Awarded Mastersdegree
Law of Universal Gravitation
W = m x g
• 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 - 1687Lucasian 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 1st 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 2nd Law
• A body will accelerate with acceleration proportional to the force and inversely proportional to the mass
F = m x a• F = Net Force (N)• m = mass (kg)• a = acceleration (m/s2 )
Momentum
p = m x v• 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.
Δ p = m x Δ vΔ p = F x Δ t
Newton’s 3rd Law
• Every action has a reaction equal in magnitude and opposite in direction
Newton’s 3rd Modelled
Some weblinks ….
• Crash Test Results• http://www.youtube.com/watch?v=zmUBgTHppv8
• NASA movie ‘Orville and Wilbur Wright’ Newton’s Laws and Flight• http://www.grc.nasa.gov/WWW/K-12/airplane/newton.html
• Space Shuttle launches• http://www.youtube.com/watch?v=4FROxZ5i67k• http://www.youtube.com/watch?v=iwfsFtpACFw&feature=related
• NASA Apollo 11 Mission• http://www.youtube.com/watch?v=LNm1LVJTJ2k&feature=related• http://www.youtube.com/watch?v=wdSPF7ujsdw&feature=related
• NASA TV• http://www.youtube.com/NASATelevision