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AP Physics Question 3

A planet has two moons, Moon and Moon , that orbit at different distances from the planet’s center, as shown.
Astronomers collect data regarding the planet, the two moons, and their obits. The astronomers are able to estimate
the planet’s radius and mass.

3. The masses of the two moons are determined to be for Moon and for Moon . It is observed that
the distance between Moon and the planet is two times that of the distance between Moon and the
planet. How does force exerted from the planet on Moon compare to the force exerted from the planet on
Moon ?

The gravitational force exerted from the planet on Moon is two times larger than the gravitational force
exerted from the planet on Moon .
B
The gravitational force exerted from the planet on Moon is eight times larger than the gravitational force
exerted from the planet on Moon .
C
The gravitational force exerted from the planet on Moon is two times smaller than the gravitational force
exerted from the planet on Moon .
D
The gravitational force exerted from the planet on Moon is eight times smaller than the gravitational force
exerted from the planet on Moon .

Sagot :

The answer is B

The gravitational force exerted from the planet on Moon is eight times larger than the gravitational force exerted from the planet on Moon .

View image eucariuswalker

Gravitational force increases as the mass increases and decreases as the distance between the bodies is increased.

  • The correct option is; The gravitational force exerted from the planet on Moon A is eight times larger than the gravitational force exerted from the planet on Moon B.

Reasons:

The given parameters are;

The moons of the planet = Moon A and Moon B

Mass of Moon A = 2·M

Mass of moon B = M

The distance between Moon B and the planet = 2 × The distance between Moon A and the planet

Required:

Comparison (compare) of the force exerted from the planet on Moon A and Moon B.

Solution:

The force, F, exerted from the planet is the gravitational force which is given by Newton's Law of Gravitation as follows;

  • [tex]\displaystyle F = \mathbf{G \cdot \frac{M_{planet} \times M}{R^2}}[/tex]

Where;

G = Universal gravitational constant

[tex]M_{planet}[/tex] = Mass of the planet

M = Mass of the Moon

R = The distance from the planet to the Moon

For Moon A, we have;

Mass = 2·M

Distance = R

Which gives;

[tex]\displaystyle F_A = G \cdot \frac{M_{planet} \times 2\cdot M}{R^2} = 2\cdotG \cdot \frac{M_{planet} \times M}{R^2} = \mathbf{2 \cdot F}[/tex]

With Moon B, we have;

Mass = M

Distance = 2·R

Therefore;

[tex]\displaystyle F_B = G \cdot \frac{M_{planet} \times M}{(2 \cdot R)^2} = G \cdot \frac{M_{planet} \times M}{4 \cdot R^2} = \frac{1}{4} \cdot G \cdot \frac{M_{planet} \times M}{R^2} = \mathbf{\frac{1}{4} \cdot F}[/tex]

Which gives;

[tex]\displaystyle \frac{F_A}{F_B} = \frac{2 \cdot F}{\frac{1}{4} \cdot F } =2 \times \frac{4}{1} = \mathbf{8}[/tex]

[tex]\displaystyle \frac{F_A}{F_B} = 8[/tex]

[tex]F_A = \mathbf{8 \times F_B}[/tex]

The force from the planet on Moon A, [tex]F_A[/tex], is 8 times the force from the planet on Moon B.

Therefore, whereby option B is;

  • The gravitational force exerted from the planet on Moon A is eight times larger than the gravitational force exerted from the planet on Moon B.

The correct option is option B

Learn more about Newton's Law of gravitation here:

https://brainly.com/question/18670622