All Questions
98
questions
1
vote
4
answers
160
views
Gravitational attraction between two bodies
While the gravitational force between two bodies is directly proportional to their masses, and inversely proportional to the distance between them is understandable / seems logical, how did Newton ...
- 123
-2
votes
1
answer
75
views
Potential energy with different heights [duplicate]
If system consists of earth and ball and ball is dropped from height $h_i$ to $h_f$, then:
$\Delta U = -(W_{earth} + W_{ball})$ ($W_{ball}$ can be neglected since it's small)
$\Delta U = -(-mg(h_f - ...
- 1
0
votes
0
answers
69
views
Dynamic equilibrium of planets
We can describe statical equilibrium ( forces, moments ) in a cuboid $$ \Sigma F_x=0,\Sigma F_y=0,\Sigma F_z=0~$$ In dynamics can we describe similar dynamic equilibrium within an inertial ...
- 1,032
2
votes
1
answer
1k
views
What does Newton's Theorem XXXIII in his book "Principia" mean?
If to the several points of a given sphere there tend equal centripetal forces decreasing in a duplicate ratio of the distances from the points; I say, that a corpuscle placed within the sphere is ...
- 870
1
vote
2
answers
47
views
Is it possible to determine if a planet can have a moon based on its mass and gravitational pull?
I'm curious, if based on what we know with Newton's law, can we determine if a random planet, knowing it's mass and gravitational pull, can hold a moon in it's orbit.
Or to phrase it another way, is ...
- 111
1
vote
2
answers
377
views
Correct explanation of tides [duplicate]
In the explanation of tides on earth there seem to be different versions for the second water bulge on the side opposite to the moon, while everybody seems to agree that the bulge on the moon side is ...
- 4,292
-1
votes
1
answer
78
views
How does a gas giant planet hold it's spherical shape when it has tidally locked rotation in it's orbit around the Sun?
How does a gas giant planet hold its spherical shape when it has a tidally locked rotation in its orbit around its Sun? Wouldn't it fall apart without its gravitational pull from the rotation? How ...
2
votes
1
answer
77
views
Falling at the centre of the Earth
Let’s assume to drill a hole at Earth surface at the point P1. The hole passes throughout the centre of the Earth and finishes at the opposite side at the point P2. Let’s assume then that 1) Earth ...
- 566
1
vote
0
answers
41
views
Did Newton derive Titius-Bode Law of the planets in his Principia? [closed]
In college I was taught that no one knows why the planetary orbits conform to the Titius-Bode Law.
Recently I read that Newton HAD figured that out in his Principia.
Right Now I can’t even find a ...
- 11
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 ...
- 2,462
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? ...
- 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 ...
- 159
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 ...
- 452
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 ...
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