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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3answers
51 views

Spring force under gravity

Why do I have to use law of conservation of energy to solve problems regarding calculation of extension in spring length when a box attached to the lower end of the spring is released from rest (such ...
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Estimate the force on your legs if you jump off a 2m high wall and land on your feet [on hold]

My final answer was 686.7N. I used F = ma, so let the mass be 70 because the average weight of a 15-year-old is near that. (the question was purposed for A-level students). 70kg x -9.81 m/s^-2 = 686....
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Central force problem

Two masses, $m$ and $2m$, orbit around their CM (center of mass). If the orbits are circular, they don’t intersect. But if they are very elliptical, they do. What is the smallest value of the ...
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Energy stored in a field - isolated system

If I consider an isolated system, e.g. two masses, i know I can apply the energy conservation principle considering the kinetic energy and the gravitational potential energy of the two masses. But to ...
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2answers
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Calculating gravitational force with multiple planets [on hold]

I have a question regarding the following problem: Given the following system of planets (see image), calculate the total gravitational force acting on $m_3$. ($m_1 = 2 \cdot 10^{20}kg;$ $m_2 = 1 \...
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Is the net force on atomic/molecular constituents of a solid body zero

So my question is this that suppose we consider a solid everyday object, say a spherical stone. Now, if I consider an atom or a molecule of the stone away from the center of the stone, then I can say ...
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How to solve a general planet orbit differential equation? [on hold]

According to Newton's gravitation law, the following differential equation can be made $$\frac{d^{2}}{d t^{2}} \mathbf{x}{\left(t \right)} = - \frac{G M }{\left|{\mathbf{x}{\left(t \right)}}\right|^{...
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1answer
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How can i obtain the correction to the eigenvalues as a result of adding the gravitational potential to the hydrogenlike atom?

In treating the hydrogen-like atoms, we normally neglect the gravitational potential for the system. I am able to justify the above statement by comparing the gravitational potential to the ...
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2answers
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Calculate escape velocity without using energy? [on hold]

Is it practically doable to calculate the escape velocity on the earth not by using the principle of energy conservation, but by calculating the velocity of the particle as a function of time using ...
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Work and gravitational potential energy in taking a book in different definition of “system” [on hold]

Can some body calculate the work done by person A in moving the book to height $h$ from ground in following three definitions of the system, where initaiial and final velocities are zero: a) only ...
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1answer
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Will arrow from traditional longbow will be dangerous if it is falling from above?

Let's imagine commonly seen in movies and video games "rain of arrows". Archers shoot up to hit enemies behind the obstacles, for example. As Brittanica states: “The best longbows were made of ...
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What is the lowest-energy configuration of a perfect fluid of constant angular momentum under gravity?

What is the lowest-energy stable configuration of a perfect (homogeneous dense incompressible inviscid) non-oscillatory fluid of constant mass and angular momentum under Newtonian self-gravity? For ...
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Verify Conservation of energy for variable gravitational field [duplicate]

Remember we can verify conversation of energy in gravitational field when we take g to be constant When we leave body from H At a point h As potential energy is mgH -mgh Kinetic energy. ...
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1answer
69 views

Verify conservation of energy in gravitational field [closed]

Remember we can verify conversation of energy in gravitational field when we take $g$ to be constant When we leave body from $H$ At a point $h$ As potential energy is $mgH -mgh$ Kinetic energy $=mv^...
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When an orbiting object is spiraling in, why do we say it is slowing down when it is really speeding up?

When one object is spiraling into another object that is rotating faster than it's orbiting because of tidal forces, isn't it its angular momentum in the frame of reference of what it's orbiting ...
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How Do I solve Newton’s law of gravity problem? $F = G (M1 * M2) / r^2$ [closed]

I have been give this problem: F=(6.67∗10−11 (Nm^2/kg^2)) ∗ ((5.64∗1024kg) (1.99∗1031kg)) / (1.51∗1015∗m)^2 I do not understand (Nm^2/kg^2) but I do understand everything else
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What are the underlying concepts in the Strength regime vs Gravity regime graph in Impact cratering? [closed]

So I am trying to write a research paper (about 3700 words) for high school about the topic in the title or something similar. I have found the following information which I am struggling to ...
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3answers
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How does an object gain energy when it enters a potential field?

Conservation of energy says total change in energy is $0$. Let's assume a small object is in outer space (maybe like a football). It moves towards a planet (assume planet has no atmosphere for ...
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1answer
35 views

Is there a Coandă effect outside the atmosphere?

For example, when air is blown through a spoon in the atmosphere, the air flow bends toward the spoon. People say it's the Coandă effect. So, outside the atmosphere, when we let air blow through the ...
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1answer
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Is an epoch-based approach valid for modeling $N$-body systems?

Consider a 3-body Newtonian system with equal masses such that velocity change at a given time epoch for a single body is given by: I am interpreting that if $\vec{R_2}$ and $\vec{R_3}$ also change ...
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Linear and rotational forces [closed]

Given a solid body accelerated by gravity, in contact with a cylinder of radius $r$, whose axis cannot translate, how to account for the forces acting on both? Assume the mass of the solid is 1 kg ...
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How would I calculate the gravity on the surface of a large rectangular solid? [closed]

This story on Reddit involves a 1 km by 1 km by 1.79 lightyear block of lead in deep space, and I was wondering if it was at all feasible (though that question is probably out of scope). To ask a more ...
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Escape Velocity - Won't the orbital path just become larger with higher initial velocity?

Escape velocity is the minimum speed needed for an object to escape from the gravitational influence of a massive body. However, gravity has infinite range. Object $A$ is always getting pulled by the ...
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2answers
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Strategy for a person throwing an object in zero G to maximize a velocity

If an astronaut is drifting away from a space station holding a wrench, they could throw it in the opposite direction in an attempt to get back. But if they do it wrong, they will only end up ...
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3answers
42 views

Accelerometer measures 1g along z-axis

I have an accelerometer which measures 1g along the z axis when resting on a table. I don't understand why this is because the net force on the accelerometer is zero along the z-axis as the force of ...
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1answer
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Is mass slowly destroyed when force of gravity is applied? [duplicate]

This may seem like a far fetched idea, but consider this system. Imagine a simple system of just the Moon orbiting around the Earth, creating low tides and high tides with its gravity. Now imagine ...
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3answers
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Why am I getting a negative sign in this derivation?

I want to derive a formula for calculating the final velocity of an object that falls from rest as it reaches the surface of the Earth. I want to take the change in acceleration into account and hence ...
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What is the mathematical approximation for uniform gravitational field in Newtonian Mechanics? [duplicate]

When measuring the local gravitational field using a simple pendulum, one of the core assumptions is that the gravitational field is homogeneous. But the theory itself (Classical/Newtonian Mechanics) ...
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1answer
25 views

Height and Velocity vertically falling body

Feynman wrote in his lecture From Newton’s Second Law we can easily tell how the object moves, and it is easy to find out how the velocity varies with time, namely, that it increases proportionally ...
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3answers
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What's wrong with this argument that the potential energy of an arbitrarily heavy object at arbitrary height is $0$?

Consider an object with mass such that there is a gravitational force downward of $1N$. Also assume the environment is a perfect vacuum. Now assume that we exert a force of $1+\epsilon $ Newton upward ...
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2answers
116 views

Newton's Universal Law of Gravitation doubt

The Universal Law of Gravitation states that the module of the force, $F$ is $$F = \frac{GmM}{r^2},$$ where $m$ and $M$ are the mass of the two objects and $r$ is the distance between the two objects....
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1answer
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Does free fall in a magnetic field also leads to no force acting on the falling object similar to free fall in gravity

In complete absence of gravity if a metallic object free falls in a magnetic field will it continuously feel the force of magnetic field or will stop feeling the magnetic field during the free fall.
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1answer
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Acceleration of free fall at different parts of Earth

“free fall is any motion of a body where gravity is the only acceleration acting upon it.” -Wikipedia Question 1 - If an object is falling freely, will it follow the Earth’s rotation too? Or will ...
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1answer
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Equator water pipeline flow at sea level?

If a water pipeline was built at sea level eg. Gulf of Mexico and the other end was at sea level in southern Chile, then the pipeline was primed with pumps, would the water then gravity feed and flow ...
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3answers
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Conceptual Question: Is acceleration due to gravity positive or negative, and if depending on the situation?

So on brilliant.org, I read a problem where they used the kinematic formula $r_y=v_0T-\frac{1}{2}gT^2$, for when $v_0=120 \frac{m}{s}$ and the magnitude of the acceleration due to gravity is $=10\frac{...
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1answer
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Will an object dropped from a high building displace due to the Earth's rotation?

I read that in the 16th and 17th century, the question of whether the Earth rotates around its axis or all celestial bodies rotate around it was extensively debated. One of the anti-rotation arguments ...
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4answers
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Is the notion of 'weight of Earth' meaningless?

I am not talking about the distinction between mass and weight, just the concept of 'weight'. In University physics (book by Young & Freedman, 14th Ed.) it is given that the weight of an object ...
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What are the conditions that an asymmetric top will perform precession in space (zero torque)?

The conditions that an asymmetric top will perform precession under gravitational field are described in the article Precession of an Unsymmetrical Top. (I can't get the full article.) But what if ...
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2answers
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Energy conservation with Newtonian gravitational fields

Suppose we have a mass $m$ in space, and we then introduce a bigger mass $M$. both have no kinetic energy initially. $M$ & $m$ attract, and move towards each other gaining some kinetic energies ...
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1answer
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How can I use Runge-Kutta4 to solve this orbit in polar coordinates?

I want to simulate a simple orbit of a planet moving around a star which is fixed in position. I have formulated the ODEs for this problem using Lagrangian Mechanics and have found the equations of ...
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1answer
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Satallite orbiting the earth [closed]

I need help understanding a question from my physics book. It goes like this: a communications firm wants to place a satellite in orbit so that it is always directly above the earth’s 45th ...
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Please explain the given statement [duplicate]

There is a statement in my physics textbook in gravitation chapter - The force of attraction due to hollow spherical shell of uniform density on a point mass situated inside it is zero Is it valid for ...
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0answers
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Accelerometer outputs vs the real accelerations [duplicate]

TL, DR : the long sentence in bold. I have been reasearching about accelerometers for a while, and I saw many times the following sentence: Accelerometers don't sense gravity, they sense every other ...
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2answers
80 views

How did Newton know gravity force between 2 objects although he could not examine it?

Yes, Isaac Newton calculated it, I know. But he could not examine the force between 2 objects (for example apple and human hand). And we all know there is gravity force between every 2 objects even ...
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1answer
29 views

Potential energy of an object (with non-negligible size compared to distance from ground level)

Let's say I have a cylindrical water tank (with area $A$ and height $h$), and the bottom of the tank is $H$ meter from the ground. So what is the potential energy of the water tank? If the $h$ is ...
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0answers
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Fine tuning of the cosmological and gravitational constants [closed]

Consider the gravitational constant $G$. According to philosopher Robin Collins, cosmologists have been able to determine a region $W_r\subseteq\mathbb{R}$ for which the universe would have permitted ...
6
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1answer
91 views

Newtonian Gravitational Waves

I was thinking about the classical equations for gravity. I got stuck on two equations: $$\vec{\nabla}.\vec{g}= 0$$ and $$\vec{\nabla} \times \vec{g}= 0$$ The first equation is Gauss law of ...
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3answers
71 views

Let's say that the Sun moves away from us, this should cause a change in gravitational force, when will this change be noticed by us?

I have studied Newtonian physics, and was having a introduction to relativistic physics. I read a similar question in 'A brief history of Time' which is now not letting me sleep.
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1answer
103 views

Are there good reasons why special relativity should motivate geometrised gravity in a way that Newtonian mechanics does not?

I have studied a bit of Newton Cartan theory recently, the geometrised version of Newtonian gravity in which gravity is due to the curvature of spacetime, but is Newtonian (simultaneity is absolute). ...
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1answer
77 views

Placement of the spaceports on our Earth

Why are spaceports located at certain points (site/place) on our Earth? Is there a physical reason I don't really know about?