Physics Review QuestionUnit:
MechanicsYear:
1993 Question#:
14Spacecraft S is traveling from planet P1 toward planet P2. At the position shown, the magnitude of the gravitational force of planet P1 on the spacecraft is equal to the magnitude of the gravitational force of plane P2 on the spacecraft. Question: If the distance X is greater than distance Y, then the mass of P1 must be: (1
) less than the mass of P2(2
) greater than the mass of P2(3
) equal to the mass of P2What is this question really asking?
Explanation by: Kristina A [ Return to question menu
]Answer 1
less than the mass of P2 INCORRECT Considering the formula m _{1}, the mass of the spaceship, is the same but in the case of r being larger
for P_{1} then m_{2} must be larger than m_{2}.
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Answer 2
greater than the mass of P2 CORRECT Using the formula: . Given that the force from each planet must be the same at the point where the spaceship is then The only way P _{1} could exert the same force as P_{2} over a longerr distance
is if P_{1} is a much larger mass.
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Answer 3
equal to the mass of P2 INCORRECT Lets use the formula: . If the masses were equal then there is no way that the distance from P _{2} could be greater.return to top
What's this question really asking?
The question is testing your knowledge of gravitational force its relationship with respect to masses and distances between objects. This relationship can be clearly represented with the formula: . F=gravitational force G= universal gravitatio constant m _{1}= mass of one object (the ship)
m_{2}= mass of another object (one of the planets)r= distance between centers. return to top |

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