Transcript Newton`s 1st Law of Motion

Newton’s 1st Law of Motion
a.k.a. The Law of Inertia
Main Idea- List on left hand
column
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What is inertia
Newton’s 1st Law Components
Force and changing direction
Forces in Equilibrium
What are balanced forces?
What is the support or normal force?
What is the SUM of Forces when forces
are balanced?
Newton’s 1st Law Video
• http://www.teachertube.com/viewVideo.ph
p?title=Newton_s_First_Law&video_id=10
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Aristotle was a Greek
Philosopher who believed
• Objects naturally move toward
a state of rest.
• Basically this means…
• That all rolling objects have a
tendency to eventually stop.
Two Thousand Years Later
• Galileo argued that Aristotle was
WRONG.
• He instead said that all objects
have the tendency to keep doing
what ever they are already doing.
• This tendency is called INERTIA
Inertia
• In objects at rest causes them to
stay at rest.
• In moving objects causes them to
stay moving at a constant speed
in a straight line.
INERTIA• The tendency for objects to
remain the same as they are.
• The inertia of an object is
related to its mass. The
greater the mass of an object
is, the greater its inertia.
Sir Isaac Newton:
British Scientist
• Sir Isaac Newton, described
the relationship between
motion and force in three
laws known as Newton’s
laws of motion.
Newton’s First Law
Components
• Part 1: An object at rest
remains at rest.
• Part 2: An object in motion
remains in motion unless
some force is acting on it.
Objects At rest
• Stay at rest
• unless something else places a FORCE
on it.
FORCE
Objects In Motion
• Will keep moving with constant velocity
• unless acted upon by an unbalanced
force.
FORCE
Since Velocity Includes Direction
• Changing Direction of an
objects motion requires
force even if the object
maintains a constant speed.
Newton’s First Law Example
• A book sliding on carpet comes to
rest because friction acts on the
book. If no net force acted on the
book, the book would continue to
move at the same velocity.
Equilibrium For Objects at
Rest
• Objects at rest are always
being acted upon by forces.
• So why don’t they start
moving?
• These forces cancel each
other out.
Balanced Forces
• Are forces that cancel each other out
and do not cause a change in motion
for the object.
THE SUPPORT FORCE
• ALSO CALLED THE
“NORMAL FORCE”
• Always pushes
perpendicular to surfaces.
• Keeps objects from falling
through those surfaces.
When Forces Are Balanced
• The sum of all force acting
on an object are 0
• ∑= Sum
• ∑ of Forces =F1 (Gravity) +
F2(Support) = 0
Balanced Forces Example
• A Box sitting on a table is
being acted upon by balanced
forces.
Support Force
F2
From Table
F1
GRAVITY
All Forces Are Equal and
Opposite So they Are…
• Balanced, they will not cause a
change in state of motion!
• The box will remain at rest…