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Competency #10

Answer and Explanation

In March 2004, Jupiter was a mere 400 million miles from the earth (this is close in astronomical terms) and could be easily seen from Earth without a telescope. In the following months, Jupiter and the earth moved farther apart from each other. As the Earth and Jupiter moved farther apart, the force of gravity of the Earth acting on Jupiter:

Answer: The correct answer is E.

1. Was equal to the force of gravity of Jupiter acting on the Earth
   
   
   This is true. We can apply Newton's Law of Universal Gravitation to determine both of these gravitational forces:
   
   
   
   We see that both of these are exactly the same!
2. Was less than the force of gravity of Jupiter acting on the Earth
   
   
   As described in Answer A above, this is not true.
3. Increased
   
   
   This is not true. Again, we can apply Newton's Law of Universal Gravitation. As these 2 planets move farther apart, their masses will remain the same. The only thing changing is the distance. As the distance increases, the force of gravity decreases. Plug in some sample numbers if this helps you see this inverse relationship.
4. Decreased
   
   
   As described in Answer C above, this is true.
5. A & D
   
   
   Since A & D are both true, this is the best answer.
6. B & D

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