Forces on an object falling to earth Question

AI Thread Summary
When an object falls toward Earth, it exerts a downward force on Earth, consistent with Newton's third law, which states that for every action, there is an equal and opposite reaction. Although the object pulls on Earth, the Earth's massive size results in an insignificant upward acceleration, making it appear as if it does not move. The gravitational force between the two bodies is mutual, but the effect on Earth is negligible due to its large mass. Understanding this dynamic clarifies why the Earth does not noticeably accelerate toward the falling object. The discussion emphasizes the importance of recognizing the interplay of gravitational forces in such scenarios.
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Homework Statement



As an object falls toward Earth

a. the object does not exert a force on earth
b. the object exerts a downward force on earth
c. Newton's third law does not apply
d. the upward acceleration of Earth is negligible because of its large mass

Homework Equations



none

The Attempt at a Solution



I chose A, but the answer for this question is d. Can someone explain how Earth accelerates?
 
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Two bodies in space always exert a gravitational force on each other, F = (G*m1*m2)/r^2 which pulls each body towards the other... this is Newton's third law, the postulate of equal/opposite forces... if the Earth exerts on a gravitational force on a falling object, that same object must reciprocate and pull on the Earth as well. this force is just far too weak for the Earth to accelerate appreciably
 
Newton's third law. The object exerts a force on the Earth equal and opposite to the force the Earth exerts on the object. Now reconsider d). Why doesn't the Earth jump up to meet the object?
 
ok, I understand now. I forgot gravity also had an opposite force.

thanks
 

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