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