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Results tagged with newtonian-gravity
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user 26076
This tag is for questions regarding the Newtonian model of gravity in which the force between two objects is given by $~GMm/r^2~.$ It is a natural phenomenon by which all things with mass or energy – including planets, stars, galaxies, and even light – attract one another. On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides.
7
votes
Didn't anybody see an apple falling before Isaac Newton?
As stated in Rijul Gupta's answer, the Newton - apple story is likely apocryphal, but there is a grain of truth in it.
As explained well in this exposition here, Newton's crucial idea was not that th …
- 89.3k
3
votes
Gravitational Field from Irregular Object
Firstly, I tried to reproduce your thin wire calculation : if you assume a wire of mass 60kg with a length of 2 metres, then I reckon the magnitude radially symmetric field near the middle of the wire …
- 89.3k
15
votes
Accepted
Platform diving: How deep does one go into the water?
The forces slowing you are (1) drag as you note and (2) buoyancy. The former, assuming ram drag is the main one, is given by:
$$F_D = -\frac{1}{2}\,A\,\rho_W\,C_D\,v^2$$
where $\rho_W$ is the densit …
- 89.3k
9
votes
What would happen if I were to fall into a massive hollow planet?
Emilio Pisanty's answer is a great one to this particular answer, i.e. there is no in principle bar from the laws of physics to a structure like yours and it would have the zero gravity inside propert …
- 89.3k
1
vote
Does the opening angle of the cone matter?
You can get all three classes of conic sections as intersections of planes which do not include the vertex with a cone of any nonzero vertex angle. You get a circle as the intersection between a plane …
- 89.3k
2
votes
Accepted
Value of of gravity 9.8m/sec^2 and centrifugal force
Strictly speaking, Newtonian dynamics problems on the Earth's surface are done in an accelerated reference frame owing to the Earth's rotation. But often this acceleration is very small: at the equato …
- 89.3k
1
vote
Does earths gravitational force vary depending on where you are on the planet?
Most certainly it does: the variation can be measured by a sensitive acceleration called a Gravimeter (see Wikipedia page with this name) and is the basis for gathering data important for minerals exp …
- 89.3k
8
votes
What is potential energy truly?
Given the law of conservation of energy, it is often evocative and helpful to imagine energy as a kind of permanent "stuff" and along with this an imagination of "where" it is.
But this doesn't alway …
- 89.3k
0
votes
How could they tell things weigh a sixth of their "Earth weight" on the moon?
"Orbits", and the observation of their properties, are the key notions here.
For example, a lunar module in a stable low Moon orbit is observed to fly at $1.3{\rm km s^{-1}}$ along the Moon's surfac …
- 89.3k
2
votes
Accepted
How did Newton figure out the law of gravity?
To answer the question in your title, he used his newly found fluxions (calculus) to prove that Kepler's laws of planetary motion imply a radial, inverse square law.
Feynman's Lost Lecture is a mixt …
- 89.3k
5
votes
Accepted
How are tidal gravity and curvature related?
I'm going to answer the question of your title, and also address the curious statement that "tidal gravity=real gravity".
Let's begin with your statement:
Tidal gravity, by my understanding, is t …
- 89.3k
6
votes
Accepted
If you could ride an elevator through the earth
Let's put a more precise description to the other answers, particularly Neil's.
First, note that there is a Gauss Law for static gravitational fields, owing to the inverse square nature of the static …
- 89.3k
0
votes
Armageddon prevention
I'd like to add a little to David Hammen's answer. As he says, the centre of mass of the asteroid-nuclear weapon system is going to pass through the Earth no matter what happens. This is true simply b …
- 89.3k
2
votes
Accepted
At what altitude above equator do gravitational and centrifugal forces cancel each other?
If you are asking the question "How high does a person have to be in order to be "weightless" because gravity is canceled from the rotation of the Earth?" as paraphrased by CoilKid, then what you are …
- 89.3k
3
votes
Accepted
Could Galileo ever prove that $g$ is the same for a feather and a hammer?
Assuming that you want to replicate David Scott's Apollo 15 version of Galileo's Tower of Pisa thought experiment, I think that something like your experiment could indeed work.
As Martin says, the …
- 89.3k