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

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String tension in vertical circular motion

Suppose that I have a point mass attached to a massless string and I am rotating it vertically. That means The mass is in uniform circular motion and the path of its motion is vertical circle. How ...
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133 views

Classical physics in curved space

I'm trying to learn General Relativity. As a stepping-stone between classic (Newtonian) physics and complete relativity, imagine a universe where space is curved, but time is perfectly flat. Also, the ...
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3answers
2k views

Does a toy top weigh less when it is spinning?

I am under the understanding that a toy top will weigh less when it is spinning. The Russians made a spinning type transport back in the 70s to lessen its payload over the tundra. Is this an effective ...
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2answers
465 views

How long will it take to fill a bath tub with oil compared to water?

As everyone knows, the oil is more viscous than water. But, I've been wondering how long it will take to fill a bath tub compared to water. It is quite obvious that oil will take longer. But, how much ...
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1answer
58 views

Deriving an equation for the mass of a pendulum (Follow up)?

Following this question: Deriving mass from simple pendulum which is summarized below Some mass $m$ is release from rest at a horizontal position. $m$ reaches the bottom of its path (so directly ...
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41 views

What is the gravitational potential at the centre of the earth?

Assuming the gravitational potential at infinity to be zero and ignoring the other celestial bodies, what is the gravitational potential at the centre of Earth? As no force acts at infinity the ...
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1answer
36 views

Find the velocity of three planets about their centre of mass

Just wanted to check if I've done this right, because it isn't working. Mercury: mass $$3.285 \times 10^23\ \mathrm{kg}$$ position: $57,910,000,000\ \mathrm{m}$ from sun Earth: mass $$5.972 \times ...
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82 views

3-body system centre of mass

I have a three body system of point masses that represent mercury, earth and the sun. I want them to orbit about a common centre of mass, but I think the centre of mass will move. I need the centre of ...
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24 views

Center of gravity of a hollow tank

I have to find the center of Gravity of a hollow oblong tank with 1 side missing. For installing lifting lugs x 4 on top which must align with the intersection point. (the tank will be lifted off the ...
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43 views

Point of zero gravity for fixed masses?

Given a number of fixed point masses in 3D space, is there necessarily one or more points where there is zero gravity (ie, the combined gravity of the masses cancels out), and, if so, how do I find ...
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Does Newtonian mechanics predict the bending of the course of light by objects with mass?

$$F=G m_1 m_2/d^2$$ $$F=ma$$ $$a_g=Gm_{\rm other}/d^2$$ In Newtonian mechanics, the acceleration of object A toward object B is not dependent on the mass of object A but on the mass of object B and ...
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417 views
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Deviation from Earth's orbit

How much orbital deviation is required for the Earth to get knocked out from current orbit so it either moves away from Sun or towards the Sun?
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60 views

Sitting to Standing Posture Transition Accelerometer Triaxial Data Explanation

I don't have a physics background. (I'm a Computer Science student) I have a waist-worn accelerometer provided by the school which is quite reliable. I've captured data of sitting still to standing ...
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2answers
190 views

Does Newtonian physics work on a galactic scale?

I'm currently working on a simulation that aims to use Newton's Law of Gravitation to simulate how a galaxy behaves gravitationally. While I haven't gotten the simulation finished yet, I have had a ...
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3answers
40 views

How gravitational force works for higher mass body with distance

$$F= \frac{G(m_1m_2)}{r^2}$$ This is the newton's universal gravitation law. Here, I want to ask how does a very very higher mass body affect the smaller body, whereas they are far away from each ...
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1answer
71 views

Spinning rubber ball with equatorial ridge

I have this rubber ball with something like a very slight equatorial ridge (sort of like Saturn's moon Iapetus) which I often spin around on my desk. I keep noticing that no matter the inclination of ...
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3answers
1k views

Actual meaning of “Gravitational Potential”?

In a gravitational field, the gravitational force acting on a body (of mass m) at a point x metres away from the attracting body (of mass M) is $\frac{GMm}{x^2}$. Integrating this force from a point ...
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2answers
389 views

Why closed bottle change its weight when I put effervescence tablet?

I use several shape, several type of material (glass, metal, plastic), I use two different balances with 0.01g of accuracy. I put oil on gasket, and put upside down (like that I can see if water ...
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3answers
432 views

Explanation of Supplee's paradox

I was reading about Supplee's paradox, which is about whether a relativistic projectile, subject to uniform gravitational acceleration, would float or sink underwater. However the solution of the ...
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2answers
108 views

Time period of a satellite close to earth

The time period $T$, of a satellite revolving around the earth and close to it is given by, $$T = \frac{2\pi r}{v}$$ where $v$ is the linear velocity of the satellite and roughly equal to $8\ \mathrm{ ...
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1answer
59 views

Why is the gravity in a mine shaft independent of depth if the local density is 2/3 of the average density? [closed]

While searching for something, I have come across the fact that the gravitational acceleration in a mine shaft is independent of depth if the local density is $2/3$ of the average density (of the ...
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45 views

What motion does this experience?

I have two Earths of $x$ distance away from each other. I place a spacecraft perpendicular to the centre of mass and the distance between the two Earths. If the Earths are fixed, then the spacecraft ...
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1answer
56 views

Minimum energy required to remove the satellite from its orbit to infinity?

My book says that minimum energy required to remove the satellite from its orbit is equal to its total energy (K.E+P.E). But shouldn't it equal to only the potential energy difference of satellite in ...
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1answer
91 views

Would an object falling on the surface of the Sun look like this? [closed]

I've been playing around with some rustic animation and then I came to simulating gravity over squishy objects, I simulated a squishy ball of unknown "squishiness" (I'm sorry I don't know a lot of ...
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4answers
512 views

Gravity between two unequal masses. Do both masses move?

I've been watching videos about gravity and I have a question My understanding is that mass have gravity and gravity is a force which attract other object with mass. For example, I jump up and the ...
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4answers
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Could we launch a missile from a planet with the mass of Jupiter?

If the Earth had the mass of Jupiter, would we be able to launch a space missile ? Is there a formula to calculate how the launch of 1-Kg payload increases with gravity?
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39 views

Why is normal force at a different location than its action forces (ie, seesaw)?

It seems very counterintuitive that the forces at the two ends also constitute the normal force at the pivot point. Does this principle apply even if the plank is tilted? (It would be good someone ...
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32 views

What is exactly gravitational potential energy and explain P.E. $= -GMm/r$? [duplicate]

I was studying gravity and I came to know about $P.E.= -\frac{GMm}{r}$ which is derived by $GMm(\frac{1}{\infty} - \frac{1}{r})$ which the work done by the body to displace it from infinity to $r$. ...
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24 views

About a cloud of charged pallets fired toward the earth

We assume there is a spacecraft that points directly to the center of the earth and it is at about 1 mil. km away from out planet. The craft has a plastic gun filled with a lot of charged plastic ...
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55 views

Deriving Kepler's First Law from Newton's Law of Universal Gravitation: Interpretation of the $u = 1/r$ change of variable

I'm working through a somewhat unsatisfying derivation of Kepler's First Law from Newton's Law of Universal Gravitation. The key to obtaining the equation of motion that you can solve lies in making ...
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108 views

Can a Set of “Maxwell's Equations” for Newtonian Gravitation be Derived from Newton's Force + Special Relativity?

When I learned about electromagnetism in my first year of undergraduate school, Maxwell's equations were derived roughly in the following way (see also here or in [1]): Gauss's law for a static ...
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1answer
72 views

Why can center of mass be used in calculating gravity?

Why can gravitational forces be based on the center of mass. Due to the fact that gravity is related to the square of the distance should not the gravitational sum of every particle exceed the force ...
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1answer
291 views

Center of mass and gravitational force

Say we have a two star system with both stars of equal mass $M$. The center of mass of this system is by definition in the center of the two stars. There is a small asteroid with mass m in orbit ...
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2answers
133 views

Why is the acceleration due to gravity $g$ quoted as if it were constant?

In elementary physics courses the value $g=9.8\:\mathrm{m/s^2}$ is used almost universally. But surely this value must depend to some extent upon one's location on the Earth. Why do we assume a ...
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0answers
51 views

Hammer will fall faster than the feather on the moon. 10 second thought experiment! [duplicate]

Please explain where my logic is wrong. a) Ignoring air, the same bowling ball will fall faster on Earth than on the Moon. b) Now, for the feather and hammer on the Moon, reverse your point of view ...
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32 views

Expression for the energy in the limit case of weak gravitational field

I'm trying to solve the following problem of General Relativity. Consider a particle of mass $m$ which moves following a geodesic in a space-time with metric $$ ds^2 = - e^{2U_n(\textbf{x})/c^2}c^...
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84 views

Direction vector for gravity

I have co-ordinate axes on the earth's surface (and I've been told these are the axes I have to use). Ignoring z, I have x and y axes. The question asks me to calculate the acceleration due to ...
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3answers
968 views

In which direction, the force of gravity directed towards?

I am not being able to answer, where is actually the force of gravity directed towards ? Look at this picture. This is a planet with the centre ‘C’. And O is an object. Every point of the planet ...
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3answers
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Similarity between the Coulomb force and Newton's gravitational force

Coulomb force and gravitational force has the same governing equation. So they should be same in nature. A moving electric charge creates magnetic field, so a moving mass should create some force ...
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1answer
43 views

Why does the Moon have circular motion while a falling apple has one-dimensional motion? [duplicate]

An apple and the Moon are both attracted to Earth. So why does the Moon have circular motion while an apple has one-dimensional motion?
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3answers
94 views

Does an object decelerate when reaching terminal velocity

I'll take the sky diver example. Right when a sky diver jumps out of the plane the net force of the diver is greatest. Then the diver begins to reach terminal velocity where the force of resistance = ...
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1answer
64 views

Is gravitational acceleration truly independent of mass?

I am doing Newtonian Physics. Correct me if I am wrong: So two objects always exert equal forces on each other(Newtons Third). So for example the same gravitational force that the earth exerts on a ...
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1answer
66 views

If Earth was split into thousands of astroid-size chucks, would any of them have gravity? [closed]

I know that mass increases gravity and that less mass decreases gravity. But is there a minimum gravity amount that won't let meteors or astroids have gravity because of their littler masses?
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2answers
275 views

Gauss law for gravitational field

Gauss's law is fundamental law of electrostatics. But Can we apply Gauss's law for Gravitational field also?
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5answers
175 views

Does gravity acting on a resting object produce any heat?

Let's compare two systems. System 1: A box is completely isolated. There are no forces acting on that object, and no interactions of any kind with other objects, waves, etc.. System 2: The same box ...
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53 views

A Magnetic Vortex in a Magnetic Vortex

This is not to scale. Can a magnetic vortex be compressed into a flat disk using magnetic entrapment? Can a magnetic vortex happen inside another magnetic vortex?
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1answer
23 views

Equation for Turning Projectile

I'm trying to cook up an equation that will give me position for a projectile which operates in the Newtonian Domain. So a the fall equation is: $$\mathbf{p_t} = \frac{\mathbf gt^2}{2} + \mathbf{v_0}...
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2answers
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Is gravitational potential always defined for a system?

I have studied about Gravitational potential energy ($GPE$) and Gravitational potential ($GP$). ..while everywhere it is said that $GPE$ is always of a system as it depends on the configuration of the ...