Questions tagged [newtonian-gravity]
The Newtonian model of gravity in which the force between two objects is given by GMm/r^2.
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Why do 2 objects, when dropped, reach the ground at the same time? [duplicate]
2 objects of the the same volume and dimensions but with different weights are dropped from a sufficient height in which said objects can reach terminal velocity. Galileo's finding was that both ...
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2answers
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What's the nicest proof that two isolates masses orbit their center of mass? [duplicate]
Although it seems intuitive, I haven't found proof of this fact in my textbooks from a purely mathematical standpoint. I was wondering if anybody knows of a particularly elegant proof of this fact, ...
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Where is the location of centre of gravity of the Earth? [on hold]
Take the Sun as a point object at the origin.
Take the Earth as a sphere centred at $x=d$ with a radius of $R$
Let $d=150,000,000,000$ m
Let $R=6,400,000$ m
Slice the sphere into vertical disks of ...
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1answer
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Formula for would something fall over or not?
Let's say I have a 10cm x 10cm x 50 cm wooden stick that weights 5kg total. The 10cm x 10cm base is touching the floor and it protrudes from the floor 50cm which is the height of the stick. Based on ...
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Formula for horizontal compression caused by tidal acceleration [closed]
I understand how tidal acceleration separates objects falling vertically into a gravitational field. This has been covered many times and derived nicely here.
$$\Delta F = 2G \frac{Mm}{r^3} \Delta r.$...
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Why doesn't the Earth slowly collapse into the Sun? [duplicate]
I understand that the sun exerts a force on the earth and that if that was the only force exerted on the earth then the earth would have already crashed into the sun a long time ago.
The reason the ...
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2answers
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Gravitational force on point mass due to uniform rod
So we have a uniform rod of mass M and length L and we have placed a point mass of mass m, which is distance a away from the midpoint of the rod.
Now setting the coordiates axes to work with, I put ...
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2answers
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A few questions on Gravity [closed]
What role does the unit vector $ \mathbf{e}_r $ play in $$ \mathbf{F} = - G \dfrac{Mm}{r^2} \mathbf{e}_r$$ and why there's a negative sign?
If the gravitational force always acting in the same ...
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1answer
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Human Body Upward Acceleration on Scale [closed]
I am reviewing for a Physics exam, and have come across the following example question:
If I weigh 200 pounds, but a scale I'm standing on reads 400 pounds,
then I am accelerating upward at
1g
2g
3g
...
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0answers
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Large mass body on Lagrange point L4/5
Lagrange points L4 and L5 are stable for a test particle. But what happens if instead the body at L4/5 (let's call it C) has a mass significant enough that its gravitational pull on the other two (let'...
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5answers
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Why is escape velocity necessary if a rocket can just move up slowly? [duplicate]
I have read multiple explanations of escape velocity, including that on Wikipedia, and I don't understand it.
If I launch a rocket from the surface of the Earth towards the sun with just enough force ...
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1answer
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How to reach $U = mgh$ Using Newton's Law of Universal Gravitation? [duplicate]
today i was curious about the potential energy, so, i started studying the Newton's Law of Universal Gravitation which its equation is \begin{eqnarray}
U= -\frac{GMm}{r}.\end{eqnarray} Well, since i ...
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3answers
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If there was a hole in the north pole to the South Pole and you jumped into it how would would you come out feet first? [closed]
If I were to dig a hole in a round sphere Say the earth starting at the north pole standing on my feet I start to dig when I come out the other side would I come out of the whole feet first or head ...
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4answers
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Kepler's third law is unintuitive
Kepler's third law states that the ratio between the period of a planet in orbit round a star squared over the average distance to that star cubed, is constant.
And in the case of an elliptical orbit, ...
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Physics behind finding center of mass of a stick like object [duplicate]
If I hold a rod with both hands wherever at opposite sides of the center of mass of the body, and bring them slowly close to each other, then the point my hands meet at, is approximately the center of ...
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1answer
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Is gravitational force different from centripetal force in projectile motion?
This has always confused me, in a projectile motion, like a cannon shooting an object, the only force acting on the body is gravitational force, which is facing downwards or more precisely, ...
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Does dark matter experience drag?
Is dark matter dragged around the galaxy by gravity as stars and groups of stars orbit the galaxy, and, if so, is its shape/distribution deformed? Similarly, would the Oort cloud be deformed by being ...
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Partition function of an asteroid gas (gravity)
Consider the classical problem (Newtonian gravity) of a large number of $N$ identical non-interacting asteroids orbiting around a big planet. I wanted to see if the problem was solvable. I wrote my ...
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3answers
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Proving that gravitational potential is work done by the object against gravity while KE increases and PE reduces
There's a person in my class who thinks that the formula for gravitational potential (-GM/r) represents the work done by gravity to move an object from infinity to any point in the gravitational field....
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What would happen if I used a jet pack that accelerates at $g$ but always upward?
I'm trying to imagine what would happens if gravity is cancelled. I assume that without air, if the effect of gravity were to disappear I would fly off Earth on a tangential line. But with the air ...
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2answers
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When would an object not be considered a point-particle in relation to gravity?
When is the Earth, for example, not considered a point in relation to gravity?
I am thinking that if one was asking a question below the crust continously to the core, then this would be an example.
...
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2answers
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Is a *difference* of potential energy relative to a frame of reference?
If we consider an electrical field, or a gravitational field, and two points in this field, is the difference of potential between this two points depending of a frame of reference ?
It seems to me ...
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gravitation (kinetic energy and angular momentum)
When a satellite in a circular orbit around the earth enters the atmospheric region it encounters small air resistance to its motion. then (1) kinetic energy increases
(2) angular momentum decreases
...
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2answers
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Which fundamental force underlies inertia? [closed]
We learn about the four fundamental forces (gravity, electromagnetism, strong, weak). I am curious about how these four forces mediate/cause/drive everyday phenomena. In particular, it has never been ...
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1answer
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Newton's theory of gravity is covariant under Galilean transformations
We know from classical mechanics that the gravitational field equation for the scalar potential takes the form $$\nabla^2\phi=4\pi \rho,$$ where $\rho$ is mass density (which, can depend on time and ...
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3answers
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Newtonian gravity equation / Big $G$; not duplicate from search results
EDIT: I apparently need to rewrite this from the RE's, but I'll leave it for continuity sake. Please read my replies for my point/question clarifications.
There are several threads regarding big G ...
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2answers
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How do you determine weights from CG when there are more than two locations
On the internet they list ways to calculate weights based on CG when there is a weight on the left and on the right of your CG.
Most of the examples show a box truck for determining the weight on the ...
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1answer
33 views
Determine corner weights of a trapezoid
Working with determining the corner weights on one axis isn't too bad.
If A is to the left of the Center of Gravity and B is to the right of the Center of Gravity. You have two equations to work with....
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2answers
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Calculation of Gravitational Potential at the centre of the cube [closed]
I came across this problem in a test and have been able to come up with a solution however I am unsure if it is correct.
I started by building a cube of twice the initial dimensions to bring point P ...
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0answers
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Estimating the Pressure of Earth's Center
The pressure of a medium of density $\rho$ and in a graviational field with strength $g$ at a depth of $z+dz$ is equal to the pressure at $z$ plus the pressure caused by the weight of a slab of volume ...
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Gravity assist, space probe
How do I calculate how close a space probe is to the sun after passing by Venus.
It is travelling with velocity $v_1 = 30 km/s$ and $\Delta v = 3 km/s$ after flying by Venus.
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3answers
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Does gravity get stronger when you climb a mountain?
As stated in the question title, what happens to the strength of the gravitational field (or equivalently, your weight) as you climb a hill or mountain? Would a weighing scale show that you were ...
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4answers
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Does an object at the center of the Earth have potential energy?
"Potential energy: The energy possessed by a body by virtue of its position relative to others, stresses within itself, electric charge, and other factors."
in other words, I think that potential ...
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3answers
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Does the gravitational field possess an inertial mass? [duplicate]
I understand that inertial mass, at least in part, comes from the inertia of energy in the zero momentum frame or rest frame of some physical system. So for a static charge the corresponding field ...
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0answers
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Application of Kepler's law [duplicate]
Suppose two equal and opposite charges are released from a relative separation of $d$ in free space.
How long would it take before they collide?
I believe we can use Kepler's law of T² being ...
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2answers
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Gravitational potential energy of a rod, attached by its end to an axis
Situation: We suppose a rod is attached by its end to some pivot, and is allowed to fall from a horizontal position. As this occurs, the rod loses gravitational potential energy ($∆U_G$), say 10J, ...
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3answers
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How did the Cavendish experiment to measure $G$ work?
I'm really confused about the Cavendish experiment.
What I'm confused about is why the rod would oscillate around the equilibrium point.
(From here on, I'm calling the balls at the end of the ...
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3answers
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What is the derivation of potential energy of an object?
I want to know why we use the gravitional force to compute the potential energy.
Assume we have a ball, and we lift it up by a distance $h$. Then, as I understand, the force $F_l$, must have been ...
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Limits on non-Newtonian gravity at length scales larger than 1 meter?
This answer from 2012 shows some information on an exponential term characterized by relative strength and range parameters $\alpha$ and $\lambda$,
One potential tested here is here
$$V(r)=-G\...
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1answer
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Velocity of an orbiting body
The velocity of an orbiting body is given by:
$$v = \sqrt{\frac{Gm}{r}}$$
I was trying to derive this formula earlier but I was struggling with incorporating $G$ into my derivation.
I tried looking ...
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0answers
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Deriving gravitational acceleration $GM/r^2$ from the Schwarzschild metric [duplicate]
Reposting this at a more active time to hopefully get an answer.
I am supposed to derive the newtonian equation for gravitational acceleration ($-GM/r^2$) from the Schwarzschild metric $$ds=-(1-\frac{...
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2answers
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Questioning whether gravity is strictly attractive. Is there a possibility for repulsion?
My teacher wanted to test our understanding before starting a new topic.
The question he gave goes something like this
“There are 2 vacuums present here about which there is an abundance of mass ...
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1answer
50 views
Deriving gravitational acceleration from the Schwarzschild metric
I am supposed to derive the newtonian equation for gravitational acceleration ($-GM/r^2$) from the Schwarzschild metric $$ds=-(1-\frac{r_s}{r})c^2dt+(1+\frac{r_s}{r})^{-1}dr+0$$ where $$r_s=\frac{2GM}{...
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0answers
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Does the $e$ in the following formula for the two-body problem represent the eccentricity?
Does the $e$ in the following formula for the two-body problem represent the eccentricity?
$$r = \frac{k^2}{cu} = \frac{k^2}{c(1+e\cos{(\theta - \theta_0))}} $$
with
$$c = \frac{Gm_2^3}{(m_1 + m_2)^2}...
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0answers
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Why spinning creates bulges? [duplicate]
Earth isnt a perfect but has bulges because of its spinning. What actually creates the bulges? Is the same reason that makes a liquid have v shape in a rotational tube?
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1answer
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Gravity on hovering objects
Imagine a remote controlled toy helicopter vertically takes off from a table and hovers at about one metre over the table that is of one metre height: hence, the total altitude is 2 metres.
What will ...
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1answer
288 views
Why can't we humans solve the three-body-problem? and why can computers solve it?
Why is it that we humans can't solve the three-body-problem? (calculate the positions of the 3 bodies in a dynamical system)
And why can computers do it?
My thoughts:
Computers do it in way smaller ...
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1answer
63 views
Two black holes colliding (classical mechanics)
I had this question come up in my exam where two identical black holes are in orbit around each other. There is a loss of energy via gravitational waves : $$\frac{d E}{d t} = kr^4\omega^6$$ where $k$ ...
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1answer
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Gravitational force on a rope
If we have a rope fixed to the ceiling. How much gravitational force will the rope experience? Let's suppose the mass is $m$.
Well the obvious answer is $mg$.
But doesn't the part that is ...
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0answers
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Derivation of gravitational field intensity of an elliptical disc about its symmetry axis [closed]
Please help me to derive the gravitational field intensity of an elliptical disc about its symmetry axis by using the gravitational field intensity of an elliptical ring.
Please don't close this ...
