Calculate terminal velocity when given cross sectional area

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SUMMARY

The discussion centers on calculating the terminal velocity of a package with an open parachute, given that the parachute increases the cross-sectional area by a factor of 31. The terminal speed of the first package, which did not have its parachute deployed, is 10 m/s. The correct approach involves using the equation R = ½CρAv², recognizing that terminal velocity squared is inversely proportional to cross-sectional area. The final answer for the terminal speed of the second package, after correcting for unit neglect, is derived from the relationship between the two packages' velocities and areas.

PREREQUISITES
  • Understanding of terminal velocity and its relationship to cross-sectional area
  • Familiarity with the equation R = ½CρAv²
  • Basic algebra skills for manipulating equations
  • Knowledge of units and dimensional analysis
NEXT STEPS
  • Study the principles of fluid dynamics related to terminal velocity
  • Learn about the effects of cross-sectional area on drag force
  • Explore the concept of proportionality in physics equations
  • Review dimensional analysis to avoid unit neglect in calculations
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Students studying physics, particularly those focusing on mechanics and fluid dynamics, as well as educators looking for examples of terminal velocity calculations.

Tatortotts
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Homework Statement


Two packages are dropped from an airplane. A parachute can increase the cross sectional area of each packages by a factor of 31. The parachute on package 1 fails to open, and the terminal speed of package 1 is 10 m/s. The parachute on package 2 opens.

What is the terminal speed of package 2 in m/s?

Homework Equations


Unsure, considering the problem gave very few numbers to work with.
R = ½CρAv2

The Attempt at a Solution


I figured since A (cross sectional area) is inversely proportional to vterminal2, that you would square package 1's vterminal (to get 100 m/s) and then divide by 31. I haven't submitted my answer yet so I'm not sure if it's right.
 
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Tatortotts said:
I figured since A (cross sectional area) is inversely proportional to vterminal2, that you would square package 1's vterminal (to get 100 m/s) and then divide by 31.
Have you left out a final step?
 
haruspex said:
Have you left out a final step?
Well, vterminal2 is proportional to 1/A, so 102 = 1/(A*31)
Solving for A I then get 1/3100 m/s, which seems a little ridiculous.
I submitted my answer (from my original solution--3.2 m/s) and it was wrong, so I know I'm missing something. I just can't seem to figure out what.
 
Tatortotts said:
Well, vterminal2 is proportional to 1/A, so 102 = 1/(A*31)
Solving for A I then get 1/3100 m/s, which seems a little ridiculous.
I submitted my answer (from my original solution--3.2 m/s) and it was wrong, so I know I'm missing something. I just can't seem to figure out what.
Here's a hint. The square of 10m/s is not 100m/s. What is it?
 
haruspex said:
Here's a hint. The square of 10m/s is not 100m/s. What is it?
Would it then be 100m2/s2? So I should take the square root of my answer?
 
Tatortotts said:
Would it then be 100m2/s2? So I should take the square root of my answer?
Yes.
 
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haruspex said:
Yes.
Thank you so much! I don't know why I decided to neglect units for that problem.
 

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