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February 21, 2026, 07:31:31 pm
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Author Topic: Gravity Question  (Read 634 times)  Share 

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aznboy50

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Gravity Question
« on: December 27, 2010, 04:39:49 pm »
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An astronaut standing on the surface of the moon experiences a gravitational force of attraction of 160N. He then moves away from the surface of the Moon to an altitude where the gravitational force is 40.

A.SOLVED
B. The astronaut now travels to another location at a height of three Moon Radii above the surface. Calculate the gravitational force at this altitude.

I keep getting ~17.7N but the answer= 10N


Thank you for any help!
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kamil9876

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Re: Gravity Question
« Reply #1 on: December 27, 2010, 05:03:01 pm »
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So initially he is a distance of away from the origin so we have:



Now he is 3r away from the surface, so he is 4r away from the centre hence the force is now:





edit: I guessed correctly that your mistake was that you read "3r away from centre" rather than "surface", indeed 160/9=17.7 and I assume that confirms my guess?
« Last Edit: December 27, 2010, 05:05:25 pm by kamil9876 »
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Voltaire: "There is an astonishing imagination even in the science of mathematics ... We repeat, there is far more imagination in the head of Archimedes than in that of Homer."

aznboy50

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Re: Gravity Question
« Reply #2 on: December 27, 2010, 05:07:35 pm »
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AHHHHH CRAP >.<
Thanks. I didn't read the question clearly enough, I was calculating as if he was 3r from the centre of mass, not the surface. THANKS

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