How Do You Calculate the Radius of the Sun Using Its Angular Size?

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Homework Help Overview

The discussion revolves around calculating the radius of the Sun based on its angular size as observed from Earth, which is approximately 0.5 degrees, with a distance of 150 million km. Participants are exploring the relationship between angular size, distance, and diameter in the context of this astronomical problem.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the setup of the equation relating angular size to diameter and distance, questioning whether the initial setup is correct. There is an emphasis on converting degrees to radians and the implications of the formula used.

Discussion Status

Some participants have provided guidance on adjusting the equation and re-evaluating the calculations. There appears to be a progression in the discussion as participants refine their approach, though explicit consensus on the final answer has not been reached.

Contextual Notes

There is a mention of confusion regarding the thread title and its relevance to the topic being discussed, indicating potential misalignment in categorization. Participants are also navigating the conversion between degrees and radians as part of their calculations.

needhelp83
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The Sun subtends an angle of about 0.5 degrees to us on the Earth, 150 million km away. What is the radius of the Sun?

theta=l/R

(2pi rad/360 degrees)0.5 degrees=2pi(150,000,000 km)

This should be simple, but the answer I get seems to not sound right at all

Have i set this up correctly?
 
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needhelp83 said:
The Sun subtends an angle of about 0.5 degrees to us on the Earth, 150 million km away. What is the radius of the Sun?

theta=l/R

(2pi rad/360 degrees)0.5 degrees=2pi(150,000,000 km)

This should be simple, but the answer I get seems to not sound right at all

Have i set this up correctly?
Why is the title of this thread rotational motion? This is something else. Your equation is correct for finding the diameter of the sun, and you do need to convert to radians as you have done. If I may change the letter for diameter to D, you have

theta = D/R

where R is the distance from the sun to the earth. Solve this for D and try your calculation again. Then remember to find the radius of the sun from D.
 
theta =D/R

(2pi rad/360°)(0.5°)=D/(150,000,000 km)

D=(1,308,997 km)

R=(1,308,997 km)/2= 654,499 km

Better?
 
needhelp83 said:
theta =D/R

(2pi rad/360°)(0.5°)=D/(150,000,000 km)

D=(1,308,997 km)

R=(1,308,997 km)/2= 654,499 km

Better?
Much better
 

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