Acceleration Due To Gravity FREE-FALL

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Acceleration Due To GravityFREE-FALL
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• You awake inside an airplane. You are somewhat
  groggy and disoriented, but comfortable with
  Northwest Airlines finest pillow keeping your
  head from banging against the unforgiving window.
  You cant help but get slightly annoyed at the
  child repeatedly kicking, punching, and head
  butting the back of your seat, but you drift off
  to sleep again, knowing full well that there are
  still many hours of flight left.

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• You are violently awoken by a strong and sudden
  urge to use the Airlines restroom. By instinct,
  you bolt upright and charge down the aisle. The
  airplane is poorly lit and most of the passengers
  are sleeping. The urge to relieve yourself is
  building, so you quickly increase your velocity.
• (Increasing your velocity is also known as what?)

Accelerating!
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• At this point you are racing down the aisle. You
  quickly turn left, savagely rip the door from its
  hinges, and take the longest step of your life
• You wonder why they would make a bathroom without
  a floor as you keep trying to step on something
  solid. And why is the bathroom so windy? Did
  someone leave the fan on or something?

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• Wait a second! That wasnt the bathroom door, it
  was the emergency exit! As the wind is rushing
  through your hair, you feel calmed by your
  understanding of the physics occurring all around
  you and you start to contemplate your interesting
  situation

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We know that objects have a speed or velocity
when they fall, but do they also accelerate?

1. Yes
2. No

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Objectives

• To find your acceleration at any time during your
  fall.
• To find your velocity at any time during your
  fall.
• To find how far youve fallen at any given time
  during your fall

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Acceleration Due to Gravity

• So this means that as you fall, you are speeding
  up or falling faster and faster.
• All objects falling towards earth Accelerate at a
  rate of 9.8 m/s2 (neglecting air resistance)

Feather and Moon Video Clip
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After falling for one second, what is your
acceleration?

1. 0 m/s2
2. 4.9 m/s2
3. 9.8 m/s2
4. 19.6 m/s2

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After falling for two seconds, what is your
acceleration?

1. 0 m/s2
2. 4.9 m/s2
3. 9.8 m/s2
4. 19.6 m/s2

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After falling for three seconds, what is your
acceleration?

1. 0 m/s2
2. 9.8 m/s2
3. 19.6 m/s2
4. 29.4 m/s2

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Objectives

• To find your acceleration at any time during your
  fall. Done
• To find your velocity at any time during your
  fall.
• To find how far youve fallen at any given time
  during your fall.

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Velocity of a Falling Object
Initial velocity

• Since the acceleration is 9.8 m/s2 of an object
  in free-fall and your velocity is in the same
  direction as the acceleration, you gain 9.8 m/s
  of speed every second!

0 m/s
vf vi gt
time
Final velocity
Acceleration due to gravity (9.8 m/s2)
a
v
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Example
t 0 s
v 0 m/s
t 1 s
v 9.8 m/s
v 19.6 m/s
t 2 s
v 29.4 m/s
t 3 s
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v 0 m/s
v
v 9.8 m/s
v 9.8 m/s
v 19.6 m/s
v 19.6 m/s
v 29.4 m/s
v 29.4 m/s
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Objectives

• To find your acceleration at any time during your
  fall. Done
• To find your velocity at any time during your
  fall. Done
• To find how far youve fallen at any given time
  during your fall.

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Distance

• Because you are going faster as you fall, the
  distance you have fallen per second is greater.
• To find the distance fallen, use the following
  formula

time
d ½ gt2
distance
Acceleration due to gravity (9.8 m/s2)
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Example
d ½ gt2
v 0 m/s
t 0 s
d 0 m
t 1 s
d ½ (9.8)(1)2
v 9.8 m/s
d 4.9 m
d ½ (9.8)(2)2
v 19.6 m/s
d 19.6 m
t 2 s
t 3 s
d ½ (9.8)(3)2
d 44.1 m
v 29.4 m/s
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Objectives

• To find your acceleration at any time during your
  fall. Done
• To find your velocity at any time during your
  fall. Done
• To find how far youve fallen at any given time
  during your fall. Done

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Rearrange distance equation