Motion

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Unit 4

• Motion

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Motion

• change in position

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Speed

• distance traveled per unit of time
• speed distance / time

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Speed

• Average speed is equal to the total distance
  traveled divided by the total time for the trip
• average speedtotal distance/total time

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Speed

• Speed at any instant is called instantaneous speed

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Velocity

• Speed and direction
• Velocity describes the speed and direction of a
  moving object

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Changes in Speed

• Speeding up and slowing down are changes in speed

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Changes in Speed

• To find a change in speed, subtract the initial,
  or starting, speed from the final speed
• change in speed
  final speed initial speed

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Acceleration

• Change in speed or direction
• An object is accelerating when it speeds up,
  slows down, or changes direction

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Acceleration

• Slowing down is sometimes called deceleration

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Acceleration

• To find acceleration, you must know the change in
  speed and the time for that change to occur
• acceleration change in speed / time or
• acceleration (final speed
  initial speed) / time

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Balanced and Unbalanced Forces

• A force is a push or pull
• To describe a force, you must know two things
• Size of the force
• Direction of the force

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Balanced Forces

• Forces that are equal in size but opposite in
  direction
• Balanced forces do not cause a change in the
  motion of objects

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Unbalanced Forces

• Forces that cause a change in the motion of an
  object

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Unbalanced forces

• Unbalanced forces can change the motion of an
  object in two ways
• When unbalanced forces act on an object at rest,
  the object will move
• When unbalanced forces act on a moving object,
  the velocity of the object will change

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Newtons First Law of Motion

• Newtons First Law of Motion states that an
  object will remain at rest, or move at a constant
  speed in a straight line, unless it is acted on
  by an unbalanced force

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Newtons First Law of Motion

• inertia tendency of an object to stay at rest
  or in motion
• Newtons First Law of Motion is also called the
  Law of Inertia

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Newtons Second Law of Motion

• Newtons Second Law of Motion describes the
  relationship among force, mass, and acceleration

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Newtons Second Law of Motion

• Unbalanced forces cause objects to accelerate
• The amount by which an object accelerates depends
  on two things
• size and direction of the force
• Mass of the object

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Newtons Second Law of Motion

• If two forces act on the same object, the larger
  force will produce more acceleration than the
  smaller force

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Newtons Second Law of Motion

• If you apply the same amount of force to two
  objects with different masses, the object with
  the smaller mass will accelerate more than the
  object with the larger mass

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Newtons Second Law of Motion

• force mass X acceleration
• F m X a
• Force is measured in Newtons (N)
• Newton unit of force equal to one
  kilogram-meter per second per second

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Newtons Third Law of Motion

• Newtons Third Law of Motion states that for
  every action force, there is an equal and
  opposite reaction force

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Newtons Third Law of Motion

• Forces always act in pairs
• The two forces act in opposite directions

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Newtons Third Law of Motion

• action force force acting in one direction
• reaction force force acting in the opposite
  direction