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					“Do noW” TemplaTe             TAPE the note sheet you were
                              handed at the door into pg. of
       STATEMENT              your interactive notebook!
             The ancient Greeks concluded that it was
              necessary to apply a continuous force to
                      keep an object in motion.
           For example, if you set a book on a table and
             give the book a quick push, the book slides
              a short way then stops. To keep the book
                 moving, you need to keep pushing it.
             The Greeks reasoned that the book stops
                 moving because you stop pushing it.
QUESTION
  Based off of information you have learned, write a brief
   paragraph letter to the Greeks, explaining what scientists
 have discovered to help the Greeks understand why the book
                         stops moving.
    A puck is moving on an
                                 THINK ABOUT THIS…
    air-table. If the table is
    so large that the puck
    never hits an edge, what
    will happen to the puck?
A      It will never stop.

B      It will stop in a short
       distance.
C      It will speed up.
   Galileo’s Thought Experiment


• Galileo thought of a different way to explain
  the observation of the motion of the book.
• He imagined a world without friction and
  conducted an experiment.

  I doubt the Greeks’
  idea! Suppose…
       Galileo’s Thought Experiment

                     The rail is
                     horizontal…

If ball-bearing is   No force is needed to
released here…       keep the ball-bearing
                     moving.
                                             …it will never rise up,
                                             and will move at
                                             constant speed.
                          horizontal rail
     Galileo’s Thought Experiment


– In the absence of friction, a moving object will
  continue moving even if there is no force acting
  on it.
– In other words it does not take a force to keep an
  object moving, it takes a force – friction – to stop
  an object that is already moving.
Newton’s 1st Law of Motion
 Description

    Objects at rest remain at
   rest, and objects in motion
    remain in motion with the
   same velocity, unless acted
      upon by an unbalanced
              force.
Newton’s 1st Law of Motion
     LAW
Newton’s 1st Law of Motion
 Additional Information

      Inertia: Tendency of an
    object to resist changes in
              motion.
  mass       inertia          Mass of an object is
     resistance to             a measure of its
   start to move from rest        inertia.
   change moving speed
       Which Has More Inertia?
Which is harder to push, pull, turn, or stop?!?
Newton’s 1st Law of Motion
     Everyday Examples




Unbalanced Force


                       Unbalanced Force




                   Object in Motion
  Object at Rest
Activity: (Name of Activity Station)


Observations:


Explanation: (Connect your observations to
Newton’s 1st Law!)
                 Exit Ticket
A ball is at rest on the floor of a car moving at a
constant velocity. What will happen to the ball
if the car swerves suddenly to the left?
Justify your answer using Newton’s Law of
Inertia.