Force and Newton’s Laws of Motion

							Force and Newton’s Laws of
          Motion
    BY: BRIANNA SHIELDS
DO NOW
  1. If a foam block and a brick are
   dropped from the roof of the school,
   which one will hit the ground first?
  2. Where on Earth could you go to
   weigh the most?
  3. When a pendulum is allowed to
   freely swing back and forth it eventually
   slows down. Why?
GOAL
  To define force and give examples of it

  To apply Newton’s Laws of Motion
Physics Current Event
   Read the article “Fantastic Physics”
    from the Current Science magazine
   Use the response starters on your ELA
    bookmark to write 3 RESPONSES to
    the article
 Force    1. Any push or pull
           2. Can do one of the following:
            – Balance each other out
            – Overpower one another
            – Work together
 Wind blowing on a flag
 Push



 A magnet attracting metal
 Pull
 Jet engine moving a plane
 Push



 Moon causing the tides
 Pull
 Nuclear explosion
 Push



 Proton and electron attracting
 Pull
 Blowing up a balloon
 Push



 Tug of war
 Pull
 Gravity
 Pull



 Closing a door
 Push or pull
  Defining Force
 2 forces in
  the same
  direction get
  added
  together
Example
  Suppose you couldn't pull a wagon of rocks
   yourself, so a friend started pulling on it with you-
   the pulling forces of you and your friend would be
   going in the same direction so you add them
   together
  Defining Force
 2 forces - one
  going one way,
  one going the
  other are
  subtracted from
  one another
                     -   =

 Object will move
  in the direction
  that the larger
  force is pointed
  towards
Example
  If a girl pulls a wagon against you in the opposite
   direction, the forces would combine by
   subtraction- The wagon would move in the
   direction of the greater force




                   Overall Mvmt
 Defining Force
 Equal but
 opposite
 forces cancel
 eachother        O
 out
Example
  If a girl pulls a wagon against you in the opposite
   direction, the forces would combine by
   subtraction- The wagon would move in the
   direction of the greater force




                   No movement
Try the Force Examples on your
handout
   Draw a picture of each scenario
   Label the forces with vectors (arrows) and
    amounts of force
   Calculate the total force
   Show the final direction of movement (if
    there is any)
   When your group is finished, raise your
    hand and I’ll check your answers
 Newton’s    An object in motion will stay in
 First Law     motion, an object at rest will stay at
 of Motion     rest, unless acted on by a force
 Newton’s    A force accelerates in the direction
 Second        of the force & is related to the
 Law of        object’s mass
 Motion       F= ma
 Newton’s    For every action, there is an equal
 Third Law     but opposite reaction (forces come
 of Motion     in pairs)
Which Law of Motion?
   When riding in a car that stops
   suddenly, your body keeps moving
   forward.
Which Law of Motion?
   The force of friction acts against an
    object’s motion.
Which Law of Motion?
   When you’re driving fast on a straight
   road and then go around a sharp curve,
   why does everyone in the car bump into
   eachother or the doors and walls?
Which Law of Motion?
   You are pushing a cart in the grocery
   store. The more force you apply (the
   harder you push) the greater the cart
   accelerates. A full cart requires a
   greater force to accelerate.
Which Law of Motion?
Which Law of Motion?
Which Law of Motion?
   The “kickback” of a gun on your
   shoulder while shooting it
Which Law of Motion?
   As you walk, your feet push on the floor
   and the floor pushes back on you
Which Law of Motion?
   Pulling a tablecloth out from beneath
   dishes without upsetting the dishes
Which Law of Motion?
Which Law of Motion?
   While stepping off a boat, the boat
   pushes away from you.
Which Law of Motion?
   If you are standing on a bus that
   suddenly moves forward, you are
   thrown off balance. Why?
Which Law of Motion?
   Why does a small car get better gas
   mileage?
Which Law of Motion?
   How much force is needed to accelerate
   a 1400 kg car 2 m/s/s?
Which Law of Motion?
Which Law of Motion?
   Push on a desk- even if it doesn’t move
   you should have a mark on you hand.
   The harder you push on it, the harder it
   pushes back
Which Law of Motion?
   Holding a bucket- you arm is holding it
   up, at the same time that gravity is
   pulling it down
Assessment
  Use the formula F= ma to solve the
  following problem: A go-cart has a
  140kg person in it. How much force
  would be required to accelerate the go-
  cart at 3m/s/s?
Assessment
  In your lab groups, come up with one of
  your own examples for each of the three
  laws of motion:
   – Newton’s 1st law of motion
   – Newton’s 2nd law of motion
   – Newton’s 3rd law of motion