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Chapter 2-2 Notes newton laws

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Chapter 2-2 Notes newton laws Powered By Docstoc
					            FOCUS 1-26-09
In Friday’s gizmo over weight and mass which
  planet had the most gravity, why is this?
Focus
 With your partner, think of an example of an
  object in your daily life that keeps on moving
  forever without anything pushing it along.
Chapter 2-2 Notes


  Newton’s Laws of Motion
Newton’s first law states that:
 An object at rest remains at rest,
 and an object in motion remains in
 motion at constant speed and in a
 straight line unless acted on by an
 unbalanced force.
Briefly explain what this    Once something
   means.
                             is moving then it
                             will keep moving
                             forever without
                             anything pushing
                             it along, until
                             something else
                             pushes or pulls it.
   At rest example:
1) A golf ball balanced on
   a tee
2) A ball on the floor


   In motion example:

1) A bowling ball rolling
2) A person in a moving
   car that stops
But objects don’t stay in    True. Friction does not
  motion forever …….          allow objects to stay in
                              motion forever. But,
                              friction is an example of
                                   Unbalanced
                              an ________________
                            __________________
                             Force
                              so Newton’s 1st law still
                              applies.
 Inertia is
 the tendency of all
 objects to resist any
 change in motion.

Example – when a car
stops, your inertia
causes you to go
forward.
How does mass impact    Small mass = less
  inertia?              inertia
                        Large mass = more
                        inertia

                        - ex:
                       Trying to throw a
                       marble or trying to
                       throw a bowling ball
 Newton’s second law of
  motion states: The
  acceleration of an object
  depends on the mass of the
  object and the amount of force
  applied.
In other words ……..    Acceleration depends
                        on how heavy an object
                        is and hard you push.

                        Acceleration depends
                        on mass and force.
State the equation used.    F=ma when F is equal
                             to force or weight, m is
Draw the circle from the     equal to mass and a is
  chalkboard here.           equal to acceleration.
                             This solves for force.
                            A=F/m this solves for
Use this to help you         acceleration
  remember the formulas.
                            M = F/a this solves for
                             mass
Practice problems:
Remember!! Write the equation, plug it in, and
solve.

Freddie is skiing. What’s his force if his mass is
  20kg and is accelerating at a rate of 5 m/s²?

F=mxa

20 kg x 5 m/s² =

100 N
2) Jon is pushing a 350 kg crate with a force of
  5N. What is the acceleration?

A=F÷m

5 N ÷ 350 kg =

0.014 m/s²
3) Jenny dropped a bowling ball that falls to the
  ground with a force of 12 Newtons. The
  acceleration of the bowling ball is 9.8 m/s²
  due to gravity. What is the mass?
m=F÷a

12 N ÷ 9.8 m/s² =

1.224 kg
Focus
 Write 2 original (don’t use the car example
  from the notes) examples of inertia.
                            Newton’s third law
                              states:
                           Whenever one object
                              exerts a force on a
                              second object, the
                              second object exerts an
                              equal and opposite
                              force on the first.
Or briefly stated as …..   All forces act in pairs. If a
                              force is exerted another
                              force occurs that is
                              equal in size and
                              opposite in direction.
Action  Reaction    Some examples are:
                      Swimmer –
                      action force = hand
                      hitting water
                      reaction force = water
                      moving
Can you always see the    No – this occurs in
  action/reaction?         nonmoving objects also

                         Example = you sitting in a
                           chair

				
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