MOTION AND SPEED

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MOTION AND SPEED

• Chapter 2

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Section 1 Describing Motion

• Motion when an object changes its position
  relative to a reference point
• Distance how far an object has moved
• Displacement distance and direction of an
  objects change of position from a starting point

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• Speed distance an object travels per unit of
  time
• Rate any change over time
• Calculation for speed speed distance/time
• Speed that doesnt change over time constant
  speed
• Speed is usually not constant usually an object
  has changing speed
• Average speed speed of motion when speed is
  changing speed total distance/total time
• Instantaneous speed speed at any given point in
  time

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• A distance-time graph displays motion of an
  object over time.
• Plot distance on vertical axis
• Plot time on horizontal axis
• Velocity speed and direction of an objects
  motion
• Motion of Earths crust is so slow we dont notice

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Section 2 - Acceleration

• Acceleration change in velocitys rate
• Positive acceleration speed is increasing
• Negative acceleration speed is decreasing
• When an object changes speed or direction, it is
  accelerating

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• Calculating acceleration
• Acceleration change in velocity/time
• Change in velocity final velocity initial
  velocity
• Unit for acceleration m/s2
• Positive acceleration positive number with a
  positive slope on a velocity-time graph
• Negative acceleration negative number with a
  negative slope on a velocity-time graph

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• Amusement park acceleration roller coasters
• Changes in speed cause acceleration
• Changes in direction cause acceleration

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Section 3 Motion and Forces

• Force a push or pull that one body applies to
  another
• A force can cause an objects motion to change
• When two or more forces combine at the same time,
  they create a net force
• Balanced forces are equal in size and opposite in
  direction
• Unbalanced forces are unequal in size and/or are
  not in the same direction

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• Inertia and mass
• Inertia an objects resistance to any change in
  motion
• Objects with greater mass have greater inertia
• Newtons first law of motion an object moving
  at a constant velocity keeps moving at that
  velocity unless a net force acts on it an object
  at rest will stay at rest unless a net force acts
  on it

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• Auto crashes the law of inertia at work
• A passenger not wearing a seat belt keeps moving
  forward at the cars speed even after the car
  stops
• A passenger wearing a seat belt slows down as the
  car slows down and stops