How Long Does Moon E Take to Orbit Planet?

  • Thread starter Thread starter Want to learn
  • Start date Start date
  • Tags Tags
    Moon Orbit Planet
AI Thread Summary
Moon E orbits a planet with an orbital radius of 4r, while Moon D orbits at radius r and takes 20 days for one complete orbit. The discussion highlights the application of Kepler's laws, particularly the third law, which relates the orbital periods of moons to their distances from the planet. It is clarified that the orbital period of Moon E cannot simply be assumed to be 80 days based on the radius alone. The correct approach involves using the ratio of the cubes of the orbital radii to determine the orbital period. Ultimately, the consensus is that Moon E's orbital period is longer than Moon D's, but not simply four times longer.
Want to learn
Messages
23
Reaction score
0

Homework Statement



Two moons orbit a planet in nearly circular orbits. Moon D has orbital radius r, and moon E has orbital radius 4r. Moon D takes 20 days to complete one orbit. How long does it take for moon E to complete one orbit


Homework Equations



None - I think


The Attempt at a Solution



I am hoping that this problem is not complicated. Since it takes 20 days for moon D with radius r, it would take 80 days for moon E with radius 4r?

Is my reasoning correct ??
 
Physics news on Phys.org
No, it isn't. What do Kepler's laws have to say about this problem?
 
Is it just 20 days the same as moon D?

A line drawn from the sun to any planet sweeps out equal areas in equal time intervals.

Does the size - radius matter then?
 
Ok the above doesn't make sense.

Then I don't know, really.
 
It's not just 20 days.

Keplers second law is only valid for the same planet or moon (and it's trivial for a circular orbit)
Try the third law.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

Calculating Angle & Speed to Reach Planet's Moon from Station Orbit
Replies
1
Views
2K
Finding distance between Earth and Moon in gravitational fields
Replies
5
Views
2K
A satellite in orbit in a system with one planet and two moons
Replies
1
Views
1K
Does the moon orbit as a classical particle?
Replies
1
Views
2K
From circular orbit to elliptical orbit
Replies
3
Views
2K
ORBIT: change in orbital distance
Replies
10
Views
2K
Time of satellite orbit around moon?
Replies
7
Views
1K
What is the gravitational acceleration on the surface of Moon B?
Replies
1
Views
2K
B The Sun's Influence on the Moon's Orbit: Is it Negligible?
Replies
4
Views
2K
How Do You Calculate the Moon's Speed and Acceleration in Its Orbit?
Replies
6
Views
3K

Hot Threads

Recent Insights

Back
Top