KINS 382, Lab 8

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KINS - 382, Lab 8

• Freefall Equations

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Background Information / Formula

• Gravity -9.8m/s² or 32ft/s², the letter g will
  represent gravity in our equations
• When looking for final Velocity we use the
  following equation Vf² Vo² 2gd or Vf Vo
  a(t)
• A - symbol by the answer indicates falling,
  symbol indicates rising.
• Time is found with

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Question 1

• A water balloon is thrown straight down from a
  bridge 80ft. above a cars windshield.
• If the initial velocity is 3.5m/s, what is the
  balloons velocity if it hits the windshield?
  (Assume there is no air resistance.)

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Answer 1

• (Step1) Convert 80ft to meters.
  80ft X 1m / 3.28ft 24.39m
• (Step2) Choose the right formula,
  Vf² Vo² 2gd (-3.5m/s)² 2g(24.39m)
• (Step3) Vf² 12.25 m²/s² (2)
  -9.8m/s²(24.39m)
• (Step4) Vf² 12.25m²/s² 478.04m²/s²
• (Step5) Vf² 490.29m²/s²
• (Step6) Vf 490.29m²/s²
• (Step7) Vf 22.14m/s

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Question 2

• Someone who is less afraid of heights then I am
  decides to jump out of an airplane and 3 s later
  his/her velocity is 25m/s.
• What will that persons velocity be at t 7 s?
• If the plane was 5,000 ft. high how long will it
  take him to land?

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Answer 2(a)

• (Step1) Choose the formula for Vf Vf Vo
  a(t)
• (Step2) Vf Vo a(t) 25m/s
  -9.8 m/s²(4s)
• (Step3) Vf 25m/s 39.2m/s 64.2m/s

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Answer 2(b)

• (Step1) t 2d/g
• (Step2) Convert 5,000ft to meters 5,000ft X
  .304m/1ft 1,520m
• (Step3) t 1,520m(2) / -9.8m/s²
• (Step4) t 3040m / -9.8m/s² 310.20s
• (Step5) t 310.20s 17.61s

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Question 3

• A cat accidentally falls off a building.
• What distance will the kitty fall and how long
  will it take for the cat to fall if the final
  velocity is 40m/s?

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Answer 3(a)

• Find d when, Vf 40m/s The
  formula is Vf² Vo² 2g(d)
• (Step1) (40m/s)² 0 2(-9.8m/s²)d
• (Step2) 1600m²/s² 0 -19.6m/s²(d)
• (Step3) 1600m²/s² 19.6m/s² 0 -19.6m/s²
  19.6m/s² (d)
• (Step4) d 81.63 meters

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Answer 3(b)

• Find t when, Vf 40m/s The
  formula is Vf Vo a(t)
• (Step1) 40m/s 0 -9.8m/s² (t)
• (Step2) 40m/s -9.8m/s² -9.8m/s² -9.8m/s²
  (t)
• (Step3) t 4.08 s

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Question 4

• Assume a student jumps off Forbes Complex and
  falls 15 ft.
• How much time is required for him/her to contact
  the ground?

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Answer 4

• Find t when, d 15ft, g -9.8m/s² The formula
  is t 2d/g
• Convert 15ft to meters 15ft X .304m/1ft 4.56 m
  
• (Step1) t 2d/g (2) 4.56m/-9.8m/s²
• (Step2) t -.93s² .96 s

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Question 5

• At 4 s into her skydive, Karen has a velocity of
  39.2 m/s.
• Find her final velocity _at_ 6 s.
• What was her average velocity between 4 and 6 s?

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Answer 5a

• Vo 39.2m/s, to 4s, tf 6s, Vf ?, V ?
• Use Vf Vo at
• Vf -39.2m/s -9.8m/s² (6s - 4s)
• Vf -39.2m/s -9.8m/s² (2sec)
• Vf -39.2m/s -19.6m/s
• Vf -58.8m/s

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Answer 5b

• Average V between 4 - 6s.
• V 1/2 (Vo Vf)
• V 1/2(-39.2m/s -58.8m/s)
• V 1/2 (-98m/s)
• V -49m/s