Motion

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Motion
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What Do We Mean By Speed?

• Exactly how fast are you running?
• How many meters do you run for each second?
• Do you always run the same number of meters each
  second?

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Speed

• The speed of an object is a measure of how
  quickly the object gets from one place to
  another.
• Speed is calculated by taking the distance
  traveled by the time taken.
• Speed distance/time
• V d/t

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Distance Verses Displacement

• Distance is how far an object has moved from its
  original starting point.
• Displacement is the distance and direction of an
  objects change in position from the starting
  point.
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Forms of the Speed Equation
Equation Gives you If you know
v d/t Speed time and distance
d vt Distance speed and time
t d/v time distance and speed
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Velocity

• Velocity is the quantity describing both speed
  and direction.
• Velocity distance/time in a specific direction
• Velocity can change without the speed changing.

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• What is the velocity of a car that traveled a
  total of 70 kilometers south in 1.2 hours?
• What is the speed of a jet plane that travels 528
  meters in 4 seconds?

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• A car is traveling 110 km/hr. How many hours
  will it take to cover a distance of 725 km?
• How many seconds will it take for a satellite to
  travel 450,000 m at a rate of 120 m/s?

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• How far, in meters, will you travel in 180
  seconds running at a rate of 6 m/s?
• The earth travels at 68,000 miles/hour as it
  moves around the sun. How many miles does the
  earth travel in one trip around the sun (8760
  hrs)?

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Challenge Problem

• If the distance covered by a jogger is 2,541
  meters through the park and the time it took to
  cover that distance was 43.6 minutes, what was
  the speed of the jogger?

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Challenge Problem

• Which object has a greater velocity, a ball
  rolling down a 3.4 meter hill in six seconds or a
  fish swimming upstream and covering 5.4 meters in
  0.4 minutes?

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Acceleration

• Acceleration is the rate of change in velocity.
  If either speed or direction changes, the
  velocity will change.
• Acceleration can occur through a change in speed
  or change in direction.

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Acceleration (2)

• Acceleration can be positive or negative. When a
  car comes to a stop, this is called deceleration.
  

The speed is decreasing, so the acceleration is
negative.
The speed is increasing, so the acceleration is
positive.
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Acceleration Formula

• a v2 v1/time or
• a vf vi/time
• v2 or vf is the final velocity
• v1 or vi is the beginning or initial velocity.

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What Does an Acceleration Value Tell You?

• If the acceleration is small, that means the
  speed is increasing very gradually. If the
  acceleration has a greater value, the object is
  speeding up more rapidly.
• If an object has zero acceleration, then it is
  traveling at a constant speed in one direction.

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Acceleration Practice Problem

• If a car is traveling at a speed of 40 m/s and
  stops within 2.5 s, what is the cars
  acceleration?
• V1
• V2
• T
• A

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Acceleration Practice Problem

• Susan stops a ball and 2 seconds later the ball
  has a speed of 20 m/s. What is the balls
  acceleration?
• V1
• V2
• T
• A

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Acceleration Practice Problem

• John goes over the top of a hill at a speed of 4
  m/s while on his bike. Four seconds later his
  speed is 24 m/s. What is his acceleration?
• V1
• V2
• T
• A

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Acceleration Practice Problem

• Sally places a ball at the top of a ramp and lets
  it go. Four seconds later the ball is moving at
  a speed of 2.4 m/s. What is the acceleration?
• V1
• V2
• T
• A

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Acceleration Practice Problem

• Dave is traveling at 20 m/s in a car when it hits
  a tree. Dave comes to a complete stop in 4
  seconds. What is his acceleration?
• V1
• V2
• T
• A

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Acceleration Practice Problem

• A cart rolling down an incline for 5.0 seconds
  has an acceleration of 4.0 m/s2. If the cart has
  a beginning speed of 2.0 m/s, what is the final
  speed?
• V1
• V2
• T
• A