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A new moon is discovered orbiting Neptune with an orbital speed of 9.3 103 m/s. Neptune's mass is 1.0 1026 kg. What is the

radius of the new moon's orbit? What is the orbital period? Assume that the orbit is circular. (G = 6.673 10-11 N.m/kg)

User Darnell
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2 Answers

6 votes

Final answer:

To calculate the radius of a new moon's orbit, the gravitational force equation is used. After finding the radius, Kepler's third law is applied to determine the orbital period. The detailed calculation requires the gravitational constant, orbital speed, and mass of Neptune.

Step-by-step explanation:

Finding the Orbital Radius and Period of a New Moon Orbiting Neptune

To find the radius of the new moon's orbit around Neptune, we can use the formula for centripetal force, which is provided by the gravitational attraction between the moon and Neptune:

F = \(\frac{mv^2}{r}\) = \(\frac{GmM}{r^2}\)

Here, m is the mass of the moon (which cancels out), M is the mass of Neptune, v is the orbital speed of the moon, r is the radius of the orbit, and G is the gravitational constant.

Rearranging the formula to solve for r, we get:

r = \(\frac{GM}{v^2}\)

Substituting the given values:

r = \(\frac{(6.673 \times 10^{-11} \text{N.m}^2/\text{kg}^2)(1.0 \times 10^{26} \text{kg})}{(9.3 \times 10^3 \text{m/s})^2}\)

After calculation, the radius (r) is obtained.

To find the orbital period (T), we use Kepler's third law:

T = \(2\pi \sqrt{\frac{r^3}{GM}}\)

By plugging in the values of r and M and simplifying, we can calculate the orbital period of the moon.

User Damn Vegetables
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3 votes

Answer:

The radius of the moon's orbit, R = 7.715 x 10⁷ m

The orbital period of the moon, T = 14.48 hr

Step-by-step explanation:

Given,

The orbital speed of the moon, v = 9.3 x 10³ m/s

The mass of Neptune, M = 1.0 x 10²⁶ Kg

The orbital velocity of the moon is given by the relation


v = \sqrt{(GM)/(r+h)} m/s

Where,

r + h = R → radius of the moon's orbit

Therefore squaring the above equation and solving for r +h. The equation becomes

r + h = GM / v²

Substituting the given values in the above equation

R = (6.673 x 10⁻¹¹ x 1.0 x 10²⁶) / (9.3 x 10³)²

= 7.715 x 10⁷ m

The radius of the moon's orbit, R = 7.715 x 10⁷ m

The orbital period of the moon is given by the relation

T = 2π/ω

= 2πR/v ∵ ω = v/r

Substituting the values in the above equation

T = (2 x π x 7.715 x 10⁷ )/ 9.3 x 10³

= 52125.72969 s

= 14.48 hr

The orbital period of the moon, T = 14.48 hr

User Cathy
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