Newton

1
Newton

• Why do objects move in the ways they do?

2
Isaac Newton

• Born in 1642 (by coincidence, the same year of
  Galileos death.
• Born very prematurely in a small town in rural
  England (never expected to survive)
• He never knew his father (he died three months
  before Isaac was born)

3

• Isaac went away to grammar school at 15
• He returned to the farm at 18, but was a terrible
  farmer
• An uncle persuaded his mother to allow him to go
  to college which he did in 1661.

Newtons Home

• He paid his way through Cambridge by waiting
  tables and cleaning rooms for wealthier students
  and faculty

4
Plague

• Just as Newton had finally been awarded a
  scholarship at Cambridge in 1665, the Plague
  invaded England. To escape its effects, Cambridge
  was shut down and Newton retired for two years in
  the countryside.

5
A Productive Time

• Newtons two years in the countryside were
  possibly two of the most productive for one
  person in the history of science.
• During this time Newton wrote that he first
  understood the law of gravitation, the law of
  optics, and invented calculus, as well as create
  his laws of motion.
• A legend is that gravity unveiled itself when an
  apple fell on his head!
• All this while only 23 and 24 years old.

6
Newtonian Motion

• Newtons famous laws on motion were collected in
  a book he reluctantly wrote called The
  Principia
• It took much convincing from Edmund Halley before
  he would publish his physics findings.

7
Newtons First Law

• We can see that this law was an extension of what
  Galileo said, so Newtons first law is also known
  as the Law of Inertia

• An object at rest tends to stay at rest and an
  object in motion tends to stay in motion with the
  same speed and in the same direction unless acted
  upon by an unbalanced force.

8
Inertia

• Inertia is the tendency of an object to remain at
  rest or in motion unless acted upon by an
  unbalanced force.
• Inertia is measured as the mass of an object (in
  Kg)
• Inertia Demos Cards n Coins Table Cloth, Heavy
  Ball Light Ball, Car Crash

9
Newtons Second Law

• Fma
• Newton gave the world a way to talk
  quantitatively about Force
• He was able to relate an objects Inertia to its
  Acceleration, based on the Force applied to it.
• F is force in the above equation and is measured
  in Newtons (named for him not by him)

10
Fma

• Think It takes a force (a push or pull) to make
  an object accelerate
• m stands for mass
• a is acceleration
• Force is the product of these.
• The unit of mass is the kilogram, the unit of
  acceleration is m/s2.
• The unit of force is therefore the product of
  these units kg m/s2 (referred to as the Newton)

11
Newton vs. Aristotle

• According to Newton, and his law Fma, an object
  needs a net force greater than zero in order to
  have any acceleration (change in velocity)
• An object at rest or traveling at a constant
  velocity has no net force acting on it (no
  acceleration)

• The airplane stays at a level height and a
  constant velocity due to the fact that all forces
  on it are balanced.

12
The Newton

• The Unit of force used in SI is the Newton.
• Since fma and mkg, and am/s²
• Fkgm/s²
• The unit kgm/s² is known as the Newton

13
Example

• What is the force on a 100 kg object accelerating
  at 9.8m/s²?
• Fma F100kg9.8m/s²
• 980 kgm/s²
• or 980 N

14
Newtons Third Law

• For every action there is an equal and opposite
  reaction.
• This explains why a rocket fires up into space,
  why astronauts can move about in space using jets
  of air, and why an object can rest on a table top.

15
Newton Paraphrase

• "We are like dwarfs sitting on the shoulders of
  giants. We see more than they do, indeed even
  farther but not because our sight is better than
  theirs or because we are taller than they. Our
  sight is enhanced because they raise us up and
  increase our stature by their enormous height"

16
Newton

• If I have seen further it is by standing on the
  shoulders of giants
• (meaning Archimedes, Aristotle, Kepler, Brahe,
  Copernicus and Galileo etc.)

17
Personality

• Newton was a classic introvert
• He could concentrate on one topic for many hours
• He loved his pet
• He was extremely modest (he refused to publish
  his work until coaxed)
• He also had many strange habits

18

• He published his work in Latin only.
• Here is a picture of his one of is notebook
  pages.