Need help with centripetal acceleration problem.

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Homework Help Overview

The problem involves calculating the magnitude of centripetal acceleration in the context of a biophysicist using an analytic ultracentrifuge. The specific parameters include a radius of 8.4 cm and a rotation speed of 6.0 x 10^4 rpm, with a requirement to express the result in terms of the acceleration due to Earth's gravity.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the calculation of centripetal acceleration and the method of expressing it in terms of g. There are questions about the reasoning behind dividing the calculated acceleration by the acceleration due to gravity.

Discussion Status

Some participants have provided guidance on how to express the final answer in terms of g, while others are questioning the accuracy of the initial radius conversion and its impact on the final result. Multiple interpretations of the problem setup are being explored.

Contextual Notes

There is a noted discrepancy regarding the conversion of the radius from centimeters to meters, which may affect the calculations. Participants are also discussing the implications of expressing acceleration in terms of g.

Imperil
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PROBLEM
A biophysicist wants to separate sub-cellular particles with an analytic ultracentrifuge. The biophysicist must determine the magnitude of the centripetal acceleration provided by the centrifuge at various speeds and radii.

Calculate the magnitude of the centripetal acceleration at 8.4cm from the centre of the centrifuge when it is spinning at 6.0 x 10^4rpm. Express your answer in terms of g (acceleration due to Earth's gravity).

MY ANSWER
r = 0.84m
f = 6.0 x 10^4rpm = 1000s

ac = 4pi^2rf^2
= 4pi^2(0.84m)(1000s)^2
= 3.32 x 10^7 m/s^2

So now that I have the centripetal acceleration I'm unsure of how to express my answer in terms of g as per the second part of the question. What I did was the following:

ac / g
3.32 x 10^7 m/s^2 / 9.8 m/s^2 = 3.39 x 10^6 m/s^2

but I am second guessing this because I really have no idea why I dividedt he acceleration by the acceleration of Earth's gravity. Could somebody shed some light on this and if I am wrong?
 
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ac / g
3.32 x 10^7 m/s^2 / 9.8 m/s^2 = 3.39 x 10^6 m/s^2

You have to wright the answer as
(ac / g)*g
3.32 x 10^7 m/s^2 / 9.8 m/s^2 = (3.39 x 10^6 )g. That is whar required.
 
Imperil said:
Express your answer in terms of g (acceleration due to Earth's gravity).

ac = 4pi^2rf^2
= 4pi^2(0.84m)(1000s)^2
= 3.32 x 10^7 m/s^2

So now that I have the centripetal acceleration I'm unsure of how to express my answer in terms of g as per the second part of the question. What I did was the following:

ac / g
3.32 x 10^7 m/s^2 / 9.8 m/s^2 = 3.39 x 10^6 m/s^2

but I am second guessing this because I really have no idea why I dividedt he acceleration by the acceleration of Earth's gravity. Could somebody shed some light on this and if I am wrong?

Some light has already been shed, but I'm just asking you this simple question: if ac was equal to, say, 4.1*9.8 m/s^2, how much would it be in terms of g?
 
Bro...The QUestion Stated that r=8.4cm, so r=0.084m not r=0.84m...Correct that and so u r answer would be one decimal off...right answer would be ac= 3.32*10^6...in terms of g = 3.39*10^5 no unit.
 

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