Estimating the Diameter of the Moon Using a Pencil - Simple Physics Problem

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Homework Help Overview

The discussion revolves around estimating the diameter of the Moon using a pencil as a blocking object. The context involves basic principles of geometry and measurements, particularly in relation to the Earth-Moon distance.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to measure the diameter of the Moon by using the end of a pencil to block its view, noting the distance to the Moon and the size of the pencil. Participants raise questions about the distance from the eye to the pencil and suggest using similar triangle theory as a potential approach.

Discussion Status

Participants are exploring the problem with some guidance offered regarding the use of similar triangles. There is an ongoing exchange of measurements and ideas, but no consensus has been reached on a specific method or solution yet.

Contextual Notes

The original poster mentions their unfamiliarity with physics, indicating a learning context. The problem setup relies on specific measurements, such as the distance to the Moon and the size of the pencil, which are critical to the discussion.

k_yup
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im new to the physics world and know this is probably an easy problem but i don't know where to start

Hold a pencil in front of your eye at a position where its end just blocks out the moon. Make approprite measurements to estimate the diameter of the moon, given that the earth-moon distance is 3.8x10^5km.

i figured that you prob had to measure the end of a pencil which i measured about 1.5 cm which is 1.5x10^-5km but i don't really know what to do from there.
 
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k_yup said:
im new to the physics world and know this is probably an easy problem but i don't know where to start

Hold a pencil in front of your eye at a position where its end just blocks out the moon. Make approprite measurements to estimate the diameter of the moon, given that the earth-moon distance is 3.8x10^5km.

i figured that you prob had to measure the end of a pencil which i measured about 1.5 cm which is 1.5x10^-5km but i don't really know what to do from there.

How far away was the pencil from your eye?
 
about 15cm
 
so use simular triangle theory?
 
k_yup said:
so use simular triangle theory?

Yes, that would do it nicely.

Sorry for late reply I guess I missed it last night when I scanned the board.

Good luck.
 

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