Newton`s Three Law of Motion

Born in England on
Christmas day 1643.
Overview
Chapter 2b
Copernican Revolution
Bubonic Plague 1665
While home for 2 years
with nothing to do he made
his most profound
discoveries and proposed
his most startling theories.
1.Newton’s Three Laws
2. Gravitation
3. Discovery of the outer
Planets
Newton's marble tomb and
monument in Westminster Abbey
Sir Edmond Halley (1656 - 1742) English astronomer
known for his study of comets, noticed that the comets of
1531, 1607, and 1682 seemed similar and hypothesized that
they were the same comet and predicted the comet would
return in 1758; when it was observed as predicted, the
comet was named Halley's Comet in his honor.
1684 – Newton was in a
discussion with Edmund Halley,
when Halley remarked “But why
do planet’s move the way they
do?” Newton astounded everyone
with the answers from his work
20 years earlier.
Isaac Newton (1643 - 1727))
1) Invented calculus to
solve mathematical
problems related to
motion
2) Discovered the three
laws of motion
3) Discovered the
universal law of
gravitation
Sec 1
Newton’s Three Law of Motion
Principia
The Mathematical
Principles of Natural
Philosophy
1687
Newton’s Three Law of Motion
1. An object at rest tends to stay at rest, and an object in
uniform motion tends to remain in that state of motion,
unless an external force is applied to it (the Law of Inertia).
2. A force causes acceleration (a change in the velocity) of
an object (F=ma).
3. For every action there is an equal and opposite reaction.
Sec 1
Newton’s First Law of Motion:
Newton’s 2nd Law of Motion:
An object continues in a state of rest or in a state of uniform
motion at a constant speed along a straight line unless
compelled to change that state by a net force.
The amount of acceleration (a) produced by a force
(F) depends on the mass (m) of the object being
accelerated.
F= m a
An astronaut
floating in
space will
continue to
float forever in
a straight line
unless some
external force
is accelerating
him/her.
Sec 1
Sec 1
Newton’s Third Laws of
Motion
For every action, there is an equal and opposite
reaction.
The same force that is
accelerating the boy forward is
accelerating the skateboard
Sec 1
backward.
Newton’s Law of Gravity 1686
Force
Moon
m1
No Force
r
Gravity
m2
Force of
Gravity
Moon’s Orbit
Force of
Gravity
Sec 2
Comets
Newton’s Law of Gravity
1686
Two bodies attract each other with
a force that is proportional to the
mass of each body and inversely
proportional to the square of the
distance between them.
! G is the gravitational
constant
! r is the distance between
the objects
!M1 and M2 are the masses
Types of Orbits
Comets
100 lb
Planets
1/4 (100 ) =25 lb
Sec 2
To help determine the paths of the planets and the forces
upon them, Newton needed a more sophisticated
mathematics than was then available. So he invented
calculus
Meaning of Kepler’s 3rd Law and Gravity
other planets “discovered.”
Msun =a3/p2
Uranus
Same value for all
planets
The year 1781
The first planet “discovered.”
William Herschel
Neptune The year 1846
First observed by Galle and d'Arrest
(based on calculations by Adams
and Le Verrier).
Pluto
The year 1930
Discovered by Clyde Tombaugh
Sec 2
Discovery of Uranus by
Sir William Herschel (1738-1822)
Discovered Uranus on March 13,
1781
"Discovered accidentally while
Herschel was surveying the stars. One
"star" seemed different and within a
year was shown to have a planetary
orbit 18 times farther from the Sun
than Earth.
" The new planet was named Uranus
after the father of Saturn in Roman
mythology.
" The planet had been observed
numerous times by other astronomers
as early as 1690, but it was thought to Uranus was discovered using
be another star.
this 15-centimeter (6-inch)
telescope designed and built
by Herschel.
Sec 3
5
Discovery of
Neptune 1846
Discovered as the
result of
irregularities in
the motion of
Uranus and was
the first planet to
be discovered on
the basis of
theoretical
calculations.
Sun’s Gravity
J. C. Adams of Britain and U. J. Leverrier of France independently
predicted the position of Neptune
it was discovered by J. C. Galle in 1846, the day after he received
Leverrier's prediction.
Pluto: Discovered 1930
by C. Tombaugh.
Clyde W. Tombaugh:
Summary of Chapter 2, cont.
1906-1997
First proposed by Percival Lowell on the
perturbations in the orbit of Uranus. He began
searching for the planet in 1905. Independent
calculations were published by W. H. Pickering
and others.
In 1929, the search for a new planet was
resumed at Lowell Observatory. On Feb. 18,
1930, Clyde W. Tombaugh discovered a transNeptunian planet.
Pluto is named for the mythical Greek god of
the underworld
First two letters of Pluto stand for Percival
Lowell
• Laws of Newtonian mechanics explained Kepler’s
observations
• Gravitational force between two masses is proportional
to the product of the masses, divided by the square of
the distance between them
Lowell's calculations now appear to have been
incorrect and predicted location was accidentally
accurate---Pluto is far too small to have detectable
influence on Neptune or Uranus
No longer considered to be a planet-reclassified as a dwarf planet
Sec 3
• Summary: Major Early Scientist
–
–
–
–
–
–
Claudius Ptolemy (140)
Nicolaus Copernicus (1473-1543)
Tycho Brahe (1546-1601)
Johannes Kepler (1571-1630)
Galileo Galilei (1564-1642)
Isaac Newton (1642-1727)
End of Chapter 2b
The Copernican
Revolution
Go to Chapter 6