Terminal Velocity and Resistive Forces problem

AI Thread Summary
The discussion revolves around a skydiver problem involving terminal velocity and resistive forces. The participant calculates the friction constant and attempts to determine the acceleration at a speed of 30.0 m/s, arriving at an acceleration of 3.921 m/s². However, this result is questioned, suggesting potential errors in significant figures or assumptions about the drag force being linear rather than quadratic. The importance of accurately applying the physics principles and understanding the nature of drag forces in high-speed scenarios is emphasized. Clarification on these points is essential for solving the problem correctly.
cheese825
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Homework Statement


A sky diver of mass 81.5 kg jumps from a slow-moving aircraft and reaches a terminal speed of 50.0 m/s.
(a) What is the acceleration of the sky diver when her speed is 30.0 m/s?

Homework Equations


mg = bv
where b is the friction constant
and v is the terminal velocity

The Attempt at a Solution


b = (81.5)(9.8) / 50
b = 15.97

(81.5)(9.8) - (15.97)(30) = remaining force, or 319.6 Newtons
319.6 N / 81.5 = 3.921

but it seems, 3.921 is not correct. I must be missing something big.
Any help would be appreciated.
 
Last edited:
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A number of things could cause your answer to be off.

Firstly, if you are entering your answers online be careful with your significant figures - online marking software can be very pedantic about such things.

Secondly, were you explicitly told that the drag force was a linear function of velocity because for large objects moving faster than a few m/s the drag force is usually a quadratic function of velocity.
 

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