Motion

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Motion
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• motion a change in position in a certain amount
  of time
• reference point a stationary object used for
  comparison
• speed change in position (distance) in a
  certain amount of time
• when we travel we stop, start, go slower and go
  faster, so the kind of speed we have is
• average speed total distance
• total time

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• To calculate speed we use the formula
• Speed distance
• time

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V e l o c i t y
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• Whenever we travel, we usually are going
  somewhere
• So, we are covering a distance in a certain
  amount of time AND in a certain direction
• This is called velocity

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• Velocity is

speed
and
direction
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• Remember, that speed and direction is velocity
• Also remember, our speed is always changing
  sometimes we go slower, sometimes faster, we
  stop, and then we begin to go. And sometimes we
  change our direction.
• Whenever we do any of the above we have changed
  our velocity

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A c c e l e r a t i o n
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• Acceleration is a change in velocity
• Memorize five simple little words to help you
  remember what acceleration is
• STOP
• GO
• FAST
• SLOW
• TURN

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• There is a formula to calculate acceleration
• a vf vi
• t
• a acceleration
• vf final speed
• vi initial speed
• t time

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• Remember, a change in our speed or direction is
  acceleration
• Remember there are 5 little words that help us
  remember when accelerations occurs

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• There are 2 instances when acceleration can be
  negative
• Those instances are when we slow and when we stop

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Momentum
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• All moving objects have momentum
• Momentum depends on an objects mass and velocity
• If either of these values is large, then the
  momentum will be large

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• Momentum can be calculated by using the formula
• Momentum mass x velocity

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Conservation of Momentum
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• The total momentum of objects remains the same
  unless outside forces act on these objects
• In other words, if one objects slows down,
  another object goes faster

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• For example

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Forces
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• A force is any push or pull

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• A force gives energy to an object, causing it to
  start moving, stop moving, or change direction

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• Forces can be
• balanced

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• Or
• Unbalanced

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• Balanced forces do not cause any change in an
  objects motion
• Unbalanced forces cause changes in an objects
  motion
• In other words, acceleration

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Combining Forces

• Sometimes forces can be applied in the same
  direction
• Sometimes in the opposite directions
• And, sometimes opposite and equal

zero
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Friction

• Friction is a force that opposes
  motion
• Friction causes moving objects to slow and
  finally stop

Friction depends on the type of surface and how
hard the surfaces are forced together
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In this diagram, the weight of the block provides
the force pressing the surfaces together. Watch
the animation carefully

• If we push the block harder and harder, the
  frictional force will increase, until it reaches
  a maximum (in this case, 2.5N). If we push
  harder still, (say, 2.6N), the block will start
  to move, because we're now pushing harder than
  the frictional force.

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Types of Friction

• Static produced by surfaces touch

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• Sliding produced by solid objects slide over
  each other

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F l u i d F r i c t i o n

• Friction exists when objects move through fluids
• Liquids and gases are fluids

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• Fluid friction is also known as "drag".
• It depends on-
• how thick the fluid is      (its "viscosity")
• the shape of the object
• the speed of the object

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• Aircraft and car designers want to reduce drag,
  so that the vehicle can go fast without having to
  waste too much fuel.
• To reduce drag, we need a shape that the fluid
  can flow past easily and smoothly, without any
  swirls (called "eddies"). This tends to mean
  using long, pointed, "streamlined" shapes.

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• Reducing friction

• Friction can be a nuisance, because it changes
  kinetic energy into heat which is usually wasted.
  Friction also tends to wear away at the surfaces,
  causing damage.
• We can reduce friction by oiling ("lubricating")
  the surfaces. This means that the surfaces no
  longer rub directly on each other, but slide past
  on a layer of oil. It's now much easier to move
  them.

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• Gravity is a force of attraction between 2
  objects
• Depends on the mass of the 2 objects and the
  distance between them

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The earth has more gravitational pull than the
moon because it has more mass
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The sun has a greater gravitational pull on Earth
than on Neptune because the Earth is closer
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Mass and Weight

• Mass the amount of particles in an object

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• Weight the result of a force (gravity) pulling
  down on an objects mass
• Weight mass x acceleration due to gravity
• w mg

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• Sir Isaac Newton
• Laws of Motion

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• Sir Isaac Newton was one of the greatest
  scientists and mathematicians
• that ever lived.

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• He was born in
• England on December 25, 1643.
• He was born the same year that Galileo died. He
  lived for 85 years.

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• Isaac Newton was raised by his grandmother. In
  Woolsthorpe.

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• He attended Free Grammar School and then went on
  to Trinity College Cambridge. Newton worked his
  way through
• college.

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• While at college he became interested in math,
  physics, and astronomy.

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• Newton received both a bachelors and masters
  degree. While Newton was in college he was
  writing his ideas in a journal.

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• Newton had new ideas about motion, which he
  called his three laws of motion. He also had
  ideas about gravity, the diffraction of light,
  and forces. Newton's ideas were so good that
  Queen Anne knighted him in 1705.

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• His accomplishments laid the foundations for
  modern science and revolutionized the world. Sir
  Isaac Newton died in 1727.

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In this lesson you will develop an understanding
of each of Newton's Three Laws of Motion.
.
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First Law of Motion
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• An object at rest will remain at rest unless
  acted on by an unbalanced force.

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• An object in motion continues in motion with the
  same speed and in the same direction unless acted
  upon by an unbalanced force.

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• This law is often called "the law of inertia".

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• The amount of inertia an object has depends on
  its mass
• That is on the amount of material present in
  the object
• The more mass, the more inertia
• The more inertia the more force it takes to
  overcome the inertia

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What does this mean?
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• This law is the same reason why you should always
  wear your seatbelt.

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• Second Law
• Of
• Motion

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• Most of the motion we see undergoes change.
• Most things start up, slow down, or curve as they
  move
• There is a change in motion in other words,
  acceleration

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• Forces cause acceleration

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• Third Law
• Of
• Motion

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• Whenever one object exertsa force on another
  object,the other object exerts an equal but
  opposite force

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Action-Reaction Pair Example
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