Question on Terminal Velocity finding time

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Homework Help Overview

The problem involves two skydivers jumping from a height of 5000m, with differing terminal velocities. Skydiver A reaches a terminal velocity of 41.53 m/s, while Skydiver B, who jumps 20 seconds later, reaches a terminal velocity of 90 m/s. The objective is to determine how long Skydiver B must dive in the head-down position to catch up with Skydiver A.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the use of kinematic equations and question the applicability of these equations given the changing acceleration until terminal velocity is reached. There are inquiries about the time taken to reach terminal velocity and the relevance of drag forces in the context of the problem.

Discussion Status

Some participants suggest focusing solely on the terminal velocities to solve the problem, while others express uncertainty about how to proceed without additional information regarding the time to reach terminal velocity. There is an ongoing exploration of assumptions regarding the behavior of the skydivers before reaching terminal velocity.

Contextual Notes

Participants note the absence of specific time data for reaching terminal velocity and the instruction to ignore the dynamics prior to achieving terminal velocity. This raises questions about the assumptions that can be made in the absence of this information.

baird.lindsay
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Homework Statement


I have two skydivers umping out of a plane at 5000m . Skydiver A is using extended arms and reaching a terminal velocity of 41.53m/s. Skydiver B jumping 20 second later headdown and reaching a terminal velocity at 90 m/s. The question is to find the time the second diver must dive in the headdown position to reach Skydiver A. I know the drag forces for each of the skydivers. Cofnused on how to find the time. The answer of the time is 37 seconds but not sure how to get there


Homework Equations


kinematics? vf=vi + at


The Attempt at a Solution



im not sure I tried using vf^2=vi^2+ 2as to find distance from the earth
but the number didnt make sense to me. I think I got 88 m from Earth to reach
terminal velocity... not sure...
 
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im not sure I tried using vf^2=vi^2+ 2as to find distance from the earth
but the number didnt make sense to me. I think I got 88 m from Earth to reach
terminal velocity... not sure...[/QUOTE]

This equation only works if you have a constant acceleration, but do you have that in this case? What about after you reach terminal velocity?

Are you given a time that it takes to reach the terminal velocity?
 
rodriguez1gv said:
im not sure I tried using vf^2=vi^2+ 2as to find distance from the earth
but the number didnt make sense to me. I think I got 88 m from Earth to reach
terminal velocity... not sure...

This equation only works if you have a constant acceleration, but do you have that in this case? What about after you reach terminal velocity?

Are you given a time that it takes to reach the terminal velocity?[/QUOTE]

no it doesnt:( but yes after if your terminal velocity...there's no time in the problem...not sure what to do..
 
You are supposed to ignore whatever happens before they reach their terminal velocities, and just use the terminal velocities to solve the problem.
 
What do you have for the drag forces?
 
voko said:
You are supposed to ignore whatever happens before they reach their terminal velocities, and just use the terminal velocities to solve the problem.

how would I go about that?
 
Assume that both divers acquire their terminal velocities immediately.
 

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