Calculating Terminal Velocity for a Falling Object with Air Resistance

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Homework Help Overview

The problem involves calculating the terminal velocity of an egg falling under the influence of gravity and air resistance. The egg's mass is given, along with a specific form of air resistance characterized by a proportionality constant.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply the terminal velocity formula but expresses concern about missing information, such as the projected area and air density. Participants discuss the forces acting on the egg and their relationship to acceleration, particularly at terminal velocity.

Discussion Status

Some participants confirm the correctness of the reasoning regarding the forces and acceleration at terminal velocity. There is an acknowledgment of the original poster's thought process, indicating a productive exchange of ideas.

Contextual Notes

The original poster notes a lack of information regarding the projected area and air density, which are typically necessary for calculating terminal velocity using the standard formula.

Arcarius
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Homework Statement


An egg of mass 0.10 kg is dropped from rest at a height h. It is known that the egg dropped experiences a force due to air resistance of the form F = -kv, where v is the velocity of the egg and k is a constant of proportionality equal to 0.01781 N*s/m. What is the terminal velocity of the egg?


Homework Equations



V = sqrt(2mg/pAC)
V_t is terminal velocity,
m is the mass of the falling object,
g is the acceleration due to gravity,
C_d is the drag coefficient,
\rho is the density of the fluid through which the object is falling, and
A is the projected area of the object.


The Attempt at a Solution


The only thing I know about terminal velocity is the formula mentioned above, but it seems to me that I'm missing information (I don't have the projected area of the object, the density of the air, etc.)
The only thing I can think of is that the air resistance covers all of these and can be substituted in, giving me V = sqrt(2mg/-kv). However, I checked this with dimensional analysis and it doesn't yield the correct units. This problem is really confusing me, so I'd appreciate any help on it!
 
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Identify the forces acting on the egg as it falls. How do the forces relate to the acceleration of the egg? At terminal velocity, what is the acceleration?
 
TSny said:
Identify the forces acting on the egg as it falls. How do the forces relate to the acceleration of the egg? At terminal velocity, what is the acceleration?
Thank you for the response!
The forces acting on it are kv going upwards and mg going downwards. I'm taking the downwards direction as positive, meaning that the net force acting on it is mg-kv which is equal to ma. So the acceleration is equal to (mg-kv)/m, and I know that it is 0 when it reaches terminal velocity. So, I got (mg-kv)/m = 0, and solving for v, I got mg/k.
Is this correct?
 
That's correct.
 
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TSny said:
That's correct.

Awesome, thank you for your help! Your questions really helped guide me :)
 

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