Falling and Air Resistance

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Falling and Air Resistance

• Reading Guide Answers
• Chapter 6.7

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Falling and Air Resistance

• 1. The accelerations of the feather and coin in
  a vacuum (no air) are the same. This would be no
  different on the moon, because the Moon has no
  air resistance. However, since the moon has less
  gravity, they would both fall slower than on
  Earth.
• 2. As the air resistance increases, the net
  force will decrease. (or as the air resistance
  decreases, the net force will increase)

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Falling and Air Resistance

• 3. The net force of an object in free fall is
  equal to the weight of the object (air resistance
  is not considered in free fall)
• 4. Air resistance is dependent upon
• A. speed
• B. frontal area exposed surface area
• 5. Air resistance can be reduced by
• A. reducing speed
• B. reducing frontal area (exposed surface area)

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Falling and Air Resistance

• 6. The elephant would experience more air
  resistance because the elephant has a much larger
  frontal area exposed to air.

The elephant catches more air!
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Terminal Velocity

• 1. Terminal speed is the maximum speed that a
  falling object will reach it occurs when the
  acceleration and net force equal zero. Terminal
  velocity differs only by the addition of
  direction of motion (down!)
• 2. Weight (gravitational force) and air
  resistance balance at terminal velocity.
• 4. A feather reaches terminal velocity so quickly
  because its frontal area is very large compared
  to its very small weight.

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• 5. Terminal velocity for a skydiver ranges from
  150 to 200 km/h. (124 mph)
• 6. Zero acceleration means that the object is no
  longer accelerating zero velocity means the
  object is at rest.
• 7. Terminal speed changes if the frontal area
  exposed to the air changes (variations in body
  orientation). If the skydiver reduces frontal
  area, the terminal speed would increase. If the
  skydiver increases the frontal area, the terminal
  speed would decrease.

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• 8. Terminal velocity for a skydiver with the
  parachute deployed ranges from 15 to 25 km/h.
• 9. As the baseball and tennis ball fall, their
  speeds will increase and the air resistance
  builds. Since the weight of the tennis ball is
  less than the baseball, the net force on the
  tennis ball decreases more quickly than the net
  force on the baseball. This causes the falling
  tennis ball to be accelerated at a progressively
  lower rate than the falling baseball.