Physics Review Question

Unit: Mechanics
Year: 1993 Question#: 14
Spacecraft 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 P2

What is this question really asking?

Explanation by: Kristina A

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Answer 1
less than the mass of P2


Considering the formula m1, the mass of the spaceship, is the same but in the case of r being larger for P1 then m2 must be larger than m2. return to top

Answer 2
greater than the mass of P2


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 P1 could exert the same force as P2 over a longerr distance is if P1 is a much larger mass. return to top

Answer 3
equal to the mass of P2
Lets use the formula: . If the masses were equal then there is no way that the distance from P2 could be greater.
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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
m1= mass of one object (the ship) m2= mass of another object (one of the planets)
r= distance between centers. return to top

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