A planet has two moons with identical mass. Moon 1 is in a circular orbit of radius r. Moon 2 is in a circular orbit of radius 2r. The magnitude of the gravitational force exerted by the planet on Moon 2 is which of the following compared with the gravitational force exerted by the planet on Moon 1?
half as large
twice as large
one-fourth as large
four times as large
the same

Respuesta :

Answer: Half as large

Explanation:

Newton's law of universal gravitation for Moon 1 is:

[tex]F_{1}=G\frac{Mm}{r^{2}}[/tex] (1)

And for Moon 2:

[tex]F_{2}=G\frac{Mm}{(2r)^{2}}[/tex] (2)

Taking into account the mass of Moon 1 is equal to the mass of Moon 2

Where:

[tex]F_{1}[/tex] is the gravitational force exerted by the planet on Moon 1

[tex]F_{2}[/tex] is the gravitational force exerted by the planet on Moon 2

[tex]G=6.674(10)^{-11}\frac{m^{3}}{kgs^{2}}[/tex] is the Gravitational Constant  

[tex]M[/tex] is the mass of the planet

[tex]m[/tex] is the mass of each Moon

[tex]r[/tex] is the distance between the planet and Moon 1

[tex]2r[/tex] is the distance between the planet and Moon 2

Dividing (2) by (1):

[tex]\frac{F_{2}}{F_{1}}=\frac{G\frac{Mm}{(2r)^{2}}}{G\frac{Mm}{(r)^{2}}}[/tex]

[tex]\frac{F_{2}}{F_{1}}=\frac{1}{2}[/tex]

Isolating [tex]F_{2}[/tex]:

[tex]F_{2}=\frac{1}(2) F_{1}[/tex]