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0 votes
1 answer
18 views

Physics of a falling body within a spherically uniform system [duplicate]

I was reading The First Three Minutes and in the book it talked about how if a stone fell in a cave deep in the Earth we could calculate it's motion as if the surface of the Earth is the surface of ...
user1070280's user avatar
2 votes
0 answers
64 views

Most stable shape if Newtonian gravity was proportional to $r^\alpha$

Consider lots of mass in isolated 3D space, close to each other. Consider that only the gravitational force (Newtonian) exists. Also consider that there is no rotational motion. It is evident that a ...
whoisit's user avatar
  • 221
0 votes
1 answer
57 views

Gravity train in other planets?

A Gravity train (https://en.wikipedia.org/wiki/Gravity_train) goes through a tunnel inside a planet that connects point A with point B. On Earth, the train would not gain enough impulse to reach the ...
vengaq's user avatar
  • 2,462
1 vote
3 answers
262 views

Does gravity cause the Earth's equatorial bulge?

The way I understand centrifugal force, I don't see how Earth's daily rotation alone would cause equatorial bulges to form. The usual explanation is that the centrifugal force increases with distance ...
arz's user avatar
  • 31
0 votes
2 answers
106 views

What force accounts for Earth's equatorial bulge in an inertial frame of reference?

I am confused as to how Earth's centrifugal effects from its daily spin can be explained from an inertial frame of reference relative to the distant stars. The usual explanation is that the ...
arz's user avatar
  • 31
2 votes
1 answer
290 views

What is the rate of change of the Moon's eccentricity?

So I know the Moon's current average eccentricity is ϵ≈0.039±0.006, but was this always the case? Was it ever increasing or decreasing, and if so is it known what the current rate of change is for it? ...
rclev's user avatar
  • 161
0 votes
0 answers
43 views

Why are the orbit of planets usually ellipses? [duplicate]

There has been a similar question about planets' orbits being ellipses but the answer circulates around how the circle is a special type of orbit which doesn't really answer my question. Elaborate ...
Aarushi Agarwal's user avatar
2 votes
1 answer
59 views

Gravitational Potential of a Slowly Spinning Planet

I'm working on a problem in Thorne & Blandford's Modern Classical Physics regarding the shape of a constant density, spinning planet (Exercise 13.5). It asks you to argue that the gravitational ...
Gianfranco Grillo's user avatar
0 votes
2 answers
3k views

Gravitational potential energy inside of a solid sphere [duplicate]

I am self-studying classical mechanics. I came across a problem which required me to calculate the gravitational potential inside of a sphere. I found in one of my textbooks that the potential energy ...
ty morr's user avatar
  • 23
0 votes
2 answers
47 views

Lopsided planet

Something that has always puzzled me about Pangaea. If we have a "roughly" spherical mass of solids, aren't two points on opposite sides approximately the same distance from the center of ...
WGroleau's user avatar
  • 369
2 votes
2 answers
146 views

A simple proof that under Newtonian gravity rotating massive bodies are ellipsoids?

Here is my attempt at deriving the shape of an idealized rotating massive body under Newtonian gravity, assuming that the gravity force points towards the center of mass and shape of the body is ...
მამუკა ჯიბლაძე's user avatar
1 vote
4 answers
94 views

A problem Understanding how a two-body system of planets starts rotating around barycentre

Consider,We are Creating a Two-body system in free space,Where no other mass exists,Let's Take First Mass M1 and hold it,Now bring Second Mass M2,hold it up,Now we are giving a suddenly impulse To M1 ...
Dheeraj Gujrathi's user avatar
1 vote
1 answer
88 views

What would happen if the Earth rotated at the rate required to achieve orbit at its radius? I.e ~7k m/s instead of ~460 m/s

To achieve a circular orbit, you need to have a velocity of $$v = \sqrt{Gm/r}$$ which is about 7 km/s at the Earth’s radius, but the Earth’s rotational speed is only about 460 m/s (by taking the ...
carleton's user avatar
  • 111
7 votes
3 answers
712 views

Would it be possible to ride a bicycle on the surface of Mars?

Could you ride a standard bicycle on the surface of mars? Assumptions: You are wearing a suit to provide life-support You are riding on a prepared smooth flat martian 'road' If you were to ride ...
Andrew Masters's user avatar
-2 votes
3 answers
149 views

Why is the shape of the orbit of the Earth as it is?

My View: I think that if the sun were only force acting on earth (as a centripetal force), the earth would have a circular orbit. Since other planets also exist , there also exists gravitational force ...
Aarushi Agarwal's user avatar

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