2. Isaac Newton
• Born on January 4, 1643, in
Woolsthorpe, England, Isaac Newton
was an established physicist and mathematician,
and is credited as one of the great minds of the
17th century Scientific Revolution. With
discoveries in optics, motion and mathematics,
Newton developed the principles of modern
physics.
3. First Law of Motion: Law
of Inertia
• Newton's first law states that every
object will remain at rest or in
uniform motion in a straight line
unless compelled to change its state
by the action of an external force.
4. Second Law of Motion: Law of
Acceleration
• The second law explains how the velocity of
an object changes when it is subjected to an
external force.
• The law defines a force to be equal to change
in momentum (mass times velocity) per
change in time.
5. Third Law of Motion: Law of
Action-Reaction
• The third law states that for every action
(force) in nature there is an equal and
opposite reaction. In other words, if object A
exerts a force on object B, then object B also
exerts an equal force on object A.
8. Aristotle
» Acient Greek philosopher Aristotle was born
circa 384 B.C. in Stagira, Greece. When he
turned 17, he enrolled in Plato’s Academy. In
338, he began tutoring Alexander the Great. In
335, Aristotle founded his own school, the
Lyceum, in Athens, where he spent most of the
rest of his life studying, teaching and writing.
Aristotle died in 322 B.C., after he left Athens
and fled to Chalcis.
10. Natural Motion
• Any motion that an object does naturally - without being forced - was
classified by Aristotle as a natural motion. Examples of natural motions
include:
• Book lying at rest on a table naturally remains at rest.
If you let go of a book it naturally falls toward the earth.
Smoke naturally rises.
The sun naturally rises in the east, crosses the sky,
• then sets in the west.
11. Violent Motion
• Aristotle classified any motion that required a
force as a "violent motion". (He did not mean
violent in the modern sense...) Examples of
violent motion include:
• Pushing a book along a table.
• Lifting a book.
12. • Basically, Aristotle's view of motion
is "it requires a force to make an
object move in an unnatural"
manner - or, more simply, "motion
requires force".
14. Galileo
» Born on February 15, 1564, in Pisa, Italy,
Galileo Galilei was a mathematics professor who
made pioneering observations of nature with
long-lasting implications for the study of
physics. He also constructed a telescope and
supported the Copernican theory, which supports
a sun-centered solar system. Galileo was
accused twice of heresy by the church for his
beliefs, and wrote books on his ideas. He died in
Arcetri, Italy, on January 8, 1642.
15. • Galileo made another discovery. He showed that
Aristotle was wrong about forces being necessary to
keep objects in motion. Although a force is needed to
start an object moving, Galileo showed that, once it is
moving, no force is needed to keep it moving except
for the force needed to overcome friction. When
friction is absent, a moving object needs no force to
keep it moving. It will remain in motion all by it self.
Rather than philosophizing about ideas, Galileo did
something that was quite remarkable at the time.
