Download Isaac Newton

Isaac Newton
• Arguably the greatest scientific genius ever.
• Came up with 3 Laws of Motion to explain the
observations and analyses of Galileo and Johannes Kepler.
• Discovered that white light was composed of many colors
all mixed together.
• Invented new mathematical techniques such as calculus
and binomial expansion theorem in his study of physics.
• Published his Laws in 1687 in the book Mathematical
Principles of Natural Philosophy.
Newton’s Laws of Motion
• Newton’s Laws provide the explanation and
allow the prediction of an object’s motion.
• An object’s motion will never change for no
reason.
• The change in an object’s motion is the result
of net force.
What is Force?
• A force is a push or pull on an object.
• Forces cause an object to accelerate…
– To speed up
– To slow down
– To change direction
Newton’s First Law
• A body in motion stays in motion at constant
velocity and a body at rest stays at rest unless
acted upon by a net external force.
• This law is commonly referred to as the Law of
Inertia.
The First Law is Counterintuitive
Net Force
• Net Force is simply the total force.
• Since force is a vector, adding forces requires
that direction be considered.
• Only the forces in the direction of motion, or,
directly opposite the motion will be added.
What is Zero Net Force?
The table pushes up on
the book.
A book rests on a table.
FT
Physics
Gravity pulls down on the
book.
FG
Even though there are forces on the book, they are balanced.
Therefore, there is no net force on the book.
SF = 0
Implications of Newton’s 1st Law
• If there is zero net force on a body, it cannot
accelerate, and therefore must move at
constant velocity, which means
– it cannot turn,
– it cannot speed up,
– it cannot slow down.
Mass and Inertia
• Chemists like to define mass as the amount of
“stuff” or “matter” a substance has.
• Physicists define mass as inertia, which is the
ability of a body to resist acceleration by a net
force.
Newton’s 2nd Law
• It takes a lot of pushing or pulling (FORCE) to
change how a big mass is moving. Example:
– A basketball filled with lead
It takes very little pushing or pulling to change
how a little mass is moving. Example:
A ping pong ball
Newton’s 2nd Law
• It is easy to accelerate a small mass
• It is difficult to accelerate a large mass.
Mass Vs Weight
• Mass is measured in kilograms (kg)
• If an object has a lot of mass, it has a lot of
inertia.
• Your weight is the measure of Gravitational
Force — or how hard does the Earth pull down
on you.
• Weight is measured in Newtons.
• One Newton = ¼ of a Pound.