What is the impact of radiant pressure by the sun on cosmic dust?

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Homework Help Overview

The discussion revolves around the impact of radiant pressure from the sun on cosmic dust, specifically focusing on calculations related to the force acting on dust particles and the necessary parameters for determining their size based on radiant pressure.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the calculations involved in determining the size of a dust particle affected by solar radiant pressure, questioning the inclusion of density in the calculations and its impact on the results.

Discussion Status

Some participants have provided guidance on the importance of including the density of the dust particle in the calculations, with one participant suggesting that using typical density estimates for cosmic dust could yield results that are more accurate. There is an ongoing exploration of different density values and their implications on the final answer.

Contextual Notes

There is a noted discrepancy in the density values used by participants, with one using the density of air and another suggesting a higher density for solid dust particles. This difference in assumptions may significantly affect the calculations being discussed.

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Homework Statement




I've solved part (a), but part (b) puzzles me as I am of 103 orders of magnitude away from the answer.



The Attempt at a Solution



Intensity on dust particle = 1600 W m-2
Earth-Sun Distance = (8*60)(3*108) = 1.44 * 1011m
Mass of Sun = 1.99 * 1030 kg
g-field strength = 6.4 * 10-3 N/kg
Force acting on dust particle = Mg = (4/3)∏R3g

Radiant force = P/c = (IA)/c = (I*∏R2)/c


(I*∏R2)/c = (4/3)∏R3g

R = (3I)/(4cρ*6.4*10-3)

The answer is 2*10-7 m
 

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unscientific said:

Homework Statement

I've solved part (a), but part (b) puzzles me as I am of 103 orders of magnitude away from the answer.

The Attempt at a Solution



Intensity on dust particle = 1600 W m-2
Earth-Sun Distance = (8*60)(3*108) = 1.44 * 1011m
Mass of Sun = 1.99 * 1030 kg
g-field strength = 6.4 * 10-3 N/kg
Force acting on dust particle = Mg = (4/3)∏R3g

Radiant force = P/c = (IA)/c = (I*∏R2)/c(I*∏R2)/c = (4/3)∏R3g

R = (3I)/(4cρ*6.4*10-3)

The answer is 2*10-7 m

Did you include the density of the dust particle in the calculation? You missed out \rho in a couple of steps, but put it into the last formula, so I'm not sure. But if you take the usual density estimates for cosmic dust into account, the result is definitely within the ballpark.
 
Curious3141 said:
Did you include the density of the dust particle in the calculation? You missed out \rho in a couple of steps, but put it into the last formula, so I'm not sure. But if you take the usual density estimates for cosmic dust into account, the result is definitely within the ballpark.

Yes, I took the density of dust as the density of air, 1.22 kg/m3..
 

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