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Forces and Motion

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Forces and Motion Forces A force is a push or a pull. Force generates energy. Objects stay in place unless a force starts them moving. A newton is a metric unit of force. – PowerPoint PPT presentation

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Title: Forces and Motion


1
Forces and Motion
2
Forces
  • A force is a push or a pull.
  • Force generates energy.
  • Objects stay in place unless a force starts them
    moving.
  • A newton is a metric unit of force.

3
Applying Force
  • How do you know what direction an object will
    move?
  • How do you know how fast an object will move?

4
What word describes how much of you there is?
Mass
5
Mass
Id eat a looott of yummy bread to gain mass!
Your mass is the amount of material that your
body contains. How can you gain mass?
6
Does something that is bigger always have more
mass?
No! Not Always!
7
Does bigger more mass?
8
Force and Mass
  • How a force affects an object depends on its
    mass.
  • Mass is the amount of material in an object.
  • Think about this would you rather push a bike or
    a car?
  • It would be much harder to get a car moving due
    to its mass.
  • It takes more force to move a large mass than a
    small mass.

9
Newtons Laws of Motion
  • 1. An object at rest remains at rest and an
    object in motion remains in motion in a straight
    line unless acted upon by a force.
  • 2. When force acts on an object, the object will
    move according to the amount of force. The
    greater the mass of the object is, the smaller
    the change in motion will be.

10
Newtons Laws
  • 3. If an object exerts a force on a second
    object, the second object will exert an equal
    force.

11
Think about it..
  • If an object is standing still, are any forces
    acting upon it?

12
Natural Forces Gravity
  • Gravity is the pull that objects have on other
    objects around them. Earth is the largest object
    in our world, the pull of its gravity is the
    strongest that we feel, but is it really that
    strong?

If you toss a ball up, gravity pulls it back
towards the ground.
13
Gravity controls.
  • A roller coasters ride
  • A divers dive
  • A skiers jump
  • A baseballs fall

14
Experiment
  • Reflection Questions
  • Which is the heavier object?
  • Which do you predict will reach the ground first
    and why?
  • Did your prediction match the results?
  • What did the experiment show and why?

15
Mass vs. Weight
Do things that have more mass always weigh more?
16
Not Always!
  • When you stand on a bathroom scale, the scale is
    made of springs. The farther down you push the
    springs, the higher the number on the scale. The
    number tells you your weight. On Earth it is
    true that the more mass you have, the more weight
    you have.

17
Pretend That You Are in Space!
Oh where, oh where, has my weight gone? Oh
where, oh where can it be?
You are floating around. You drift over to a
floating bathroom scale and put your feet on it.
Your feet do not push down on the scale at all.
The scale shows that you weigh 0. You have lost
your weightbut did you lose your mass?
18
Summing up Mass and Weight
  • Your MASS is the amount of material in your body.
  • Your MASS doesnt depend on where you are.
  • Your WEIGHT is how much your body pushes down on
    a scale.
  • Your WEIGHT depends on how much MASS you have and
    where you are.
  • Weight changes on other planets and depends on
    the force of gravity.

19
Another Natural Force
  • Friction is a force that resists the motion of
    objects.
  • Friction can slow down motion and even stop it.
  • This force is always present when one surface
    touches another.
  • Ex. of friction the sole of your shoes on the
    ground, brakes on a bike, and a ball rolling on
    the grass.
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