BR Test 1 phys sciences question 6

[2010premed]

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If a pendulum were placed over a large iron ore deposit under the Earth’s surface, what change would be observed in its period?
A.The period of the pendulum would be shorter, because the density of the iron ore beneath it would slightly increase the fraction of its acceleration that is due to gravity.
</SPAN>B. The period of the pendulum would be longer, because the density of the iron ore beneath it would slightly decrease the fraction of its acceleration that is due to gravity.
</SPAN>
Answer: A

How would I know this?

 

[2010premed]

any takers?

 

[fizzgig]

my guess here is that you're supposed to recognize that acceleration due to gravity is based on earth being a big homogeneous ball of mass m... if you sit over a gigantic dense deposit, you're sorta sitting over more mass than you should be, because really the earth isn't homogeneous. given that you're sitting next to more mass than you should be the force would go up. since it specifically points you to density you should look at it this way i think. but i can reason anything AFTER the fact.. :/

 

[2010premed]

thanks =)