All Questions
42
questions
4
votes
4
answers
343
views
What is the relationship between gravitation, centripetal and centrifugal force on the Earth?
I'm trying to analyze a situation wherein a ship is moving across the surface of the earth. I am trying to analyze this situation in a reference frame that is rotating with the earth (NED frame).
I am ...
- 311
0
votes
1
answer
21
views
Can we treat the entire mass of the spheroid as being concentrated at its center?
I know that to find the gravitational force between two objects, if either of them is a sphere, we can assume its mass to be concentrated at its center and use the formula for gravitational forces for ...
- 69
0
votes
1
answer
59
views
What is the hydrostatic shape of an ideal rotating planet? [duplicate]
It is a well-known fact that rotating planets have a flattened spheroidal shape. However, the NASA site says about Haumea:
The fast spin distorts Haumea's shape, making this dwarf planet look like a ...
- 866
0
votes
3
answers
345
views
If the Earth rotated slower about its axis, would your apparent weight increase or decrease?
The title above was a question on an exam that was marked wrong for me. I answered that if the Earth rotated slower (i.e. longer days), my apparent weight would increase. I based this on the ...
- 135
0
votes
1
answer
92
views
Change in $g$ effective due to rotation
$g$ effective at any latitude changes due to rotation of earth. Does it also change due to rotation when the body is at height or at depth or does it change only at the surface?
Edit: I am referring ...
- 69
14
votes
9
answers
7k
views
Is Earth really flattened at the poles because of centrifugal force?
My question is pretty much all in the title. I was always told that our planet is flattened at its poles due to the centrifugal force generated by its own rotation. However I don’t see how centrifugal ...
- 427
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 ...
- 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 ...
- 31
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 ...
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 ...
- 513
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 ...
- 111
3
votes
2
answers
175
views
On a Torus World and the force upon inhabitants
I am looking into torus worlds for fiction, and I know how to calculate the necessary speed to rotate, and necessary radius, for such a world to get a specific force of gravity.
But what I am ...
- 221
0
votes
2
answers
214
views
Simplest expression for gravitational flattening of Earth-like planet, from zero rotation rate to Earth rate, to within 10 percent error
Richard Fitzpatrick discusses the rotational flattening of a celestial body. A model that assumes homogenous density arrives at a difference between the Earth's equatorial and polar radii of 27.5 ...
- 21.4k
1
vote
2
answers
1k
views
Difficulty understanding why acceleration of free fall is lower at the equator than the poles
I have been told that the acceleration of free fall is lower at the equator than at the poles, and that this has to do with the fact that at the equator, you are moving with circular motion so ...
- 187
0
votes
3
answers
409
views
Why are planets not torn apart?
There are two forces we know, Centripetal force (or Gravity) and Centrifugal force. Both are applied to all the planets including earth. Planets are kind of spherical due to gravitational force but ...
- 413