Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [newtonian-gravity]

The Newtonian model of gravity in which the force between two objects is given by GMm/r^2.

-2
votes
0answers
37 views

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 ...
0
votes
2answers
54 views

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, ...
0
votes
1answer
52 views

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 ...
1
vote
1answer
43 views

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 ...
-2
votes
0answers
55 views

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.$...
-1
votes
1answer
44 views

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 ...
0
votes
2answers
31 views

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 ...
1
vote
2answers
63 views

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 ...
0
votes
1answer
52 views

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 ...
0
votes
0answers
22 views

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'...
13
votes
5answers
3k views

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 ...
0
votes
1answer
54 views

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 ...
-1
votes
3answers
95 views

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 ...
1
vote
4answers
113 views

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, ...
0
votes
0answers
26 views

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 ...
0
votes
1answer
35 views

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, ...
0
votes
0answers
30 views

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 ...
3
votes
0answers
33 views

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 ...
1
vote
3answers
63 views

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....
0
votes
0answers
43 views

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 ...
0
votes
2answers
59 views

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. ...
1
vote
2answers
62 views

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 ...
0
votes
0answers
25 views

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 ...
2
votes
2answers
81 views

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 ...
2
votes
1answer
432 views

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 ...
0
votes
3answers
83 views

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 ...
1
vote
2answers
34 views

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 ...
1
vote
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....
1
vote
2answers
41 views

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 ...
1
vote
0answers
47 views

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 ...
-1
votes
0answers
21 views

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.
2
votes
3answers
85 views

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 ...
0
votes
4answers
62 views

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 ...
0
votes
3answers
203 views

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 ...
0
votes
0answers
17 views

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 ...
0
votes
2answers
42 views

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, ...
2
votes
3answers
114 views

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 ...
0
votes
3answers
45 views

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 ...
1
vote
0answers
56 views

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\...
0
votes
1answer
38 views

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 ...
-1
votes
0answers
22 views

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{...
1
vote
2answers
92 views

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 ...
0
votes
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}{...
-1
votes
0answers
23 views

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}...
0
votes
0answers
11 views

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?
0
votes
1answer
33 views

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 ...
1
vote
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 ...
1
vote
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 $k$ ...
0
votes
1answer
46 views

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 ...
-1
votes
0answers
45 views

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 ...