All Questions
Tagged with newtonian-gravity energy
125
questions
2
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75
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Gravitational collapse - proof that energy dissipation is required?
As an undergraduate, I took a short course on astrophysics, where I encountered the Jeans mass. This is the critical mass for a spherical cloud of interstellar gas above which the cloud is predicted ...
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1
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80
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Where am I wrong in proving that force perpendicular to motion increases speed and kinetic energy? [closed]
Lets think of a helicopter flying at some height $h$. It throws a food packet to a person on the ground from air. Let's neglect the air drag.
The food packet is thrown only with some velocity $v_x$ in ...
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2
votes
2
answers
111
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Why do higher objects have a greater force?
We did an experiment in class today using a spring scale, a plastic bag, and a variety of other objects. Essentially, we attached the bag to the spring scale and measured the force, in newtons, of ...
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2
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Thought experiment: Where does potential energy come from if matter is created from energy?
Let's do a thought experiment:
Assume that I have a machine that can convert energy into matter with 100% efficiency i.e. it can create any amount of matter in a small space so long as I pay it's ...
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0
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Can the gravitational singularities of black holes be solved by potential or self-energy?
In Newtonian Mechanics, the energy density of gravitational field is negative in comparison with the positive energy density assigned to mass density, meaning that that the total positive energy of ...
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Describe the decrease in potential energy if two forces are acting on it one conservative which is greater than other applied by us in opposite dirn [closed]
So imagine this situation.
An object is experiencing two forces, one due to gravity in downward direction and other applied by us in upward direction such that our force is less than gravitational ...
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3
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426
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How does gravitational potential energy work in a very large distance?
Consider a thought experiment (that I made when I was in high school) involving a universe with only two objects: a massive planet and a small asteroid. Initially, they are millions of light-years ...
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3
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113
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How does gravity do work to a horizontal projectile?
Suppose a ball is moving in a horizontal projection with some velocity $u_0$ in the positive $x$ direction. Here we see that although gravity is perpendicular to the velocity vector, it changes the ...
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393
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Relationship between height and mass?
Objects with different masses are placeed on the horizontal surface of a table. The objects are then raised to different heights above the tabel. The gain in gravitational potential energy of each ...
1
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1
answer
336
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How to calculate the energy in a hyperbolic orbit?
I'm recently reading a book about rocket science which involved orbital mechanics. I know that in an elliptical orbit, the energy $ E=-\frac{GMm}{2a}$, and therefore can get the vis-viva equation: $ ...
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12
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5
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Why is cycling easier while standing on the pedals?
On high slopes and rugged terrains, riding a bicycle while standing on the pedals is easier. Even though I cannot physically define what is "easy"; since it is a feeling that my body ...
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Increase in the internal energy of the block-surface system due to friction [closed]
I found this question:
https://plainmath.net/force-motion-and-energy/13968-block-dragged-horizontal-surface-acting-degree-horizontal-displaced
and I'm trying to understand why he used this formula to ...
0
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2
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55
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Work done by gravity confusion
Say we had an object at height $h$ in a gravitational field, and of mass $m$, its GPE would equal $mgh$, now say we dropped it and it fell a distance of $h$, the work done on the object would be equal ...
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48
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$N$-body simulation: total energy is conserved, but what about the energy of a specific particle? [closed]
It is clear that the total energy in a full gravitating $N$-body simulation should be conserved, but what about the energy of an individual particle? Is this not conserved, since the potential is ...
1
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1
answer
61
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How to find amount of energy which goes to heat in a system of damped springs in a gravity field?
I am writing a simple computer simulation of a system (in 2 dimensions), with several circular bodies. They all affect each other by their gravity and some of them are connected via damped springs (...
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2
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Constant energy in universe and spacecraft accelerating [duplicate]
Given that the energy in the universe is constant, how is it that spacecrafts traveling far distances sometimes get a boost by falling into the gravitational field of a planet? Acceleration caused by ...
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212
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Why does GPE convert to kinetic energy? [closed]
What is it about GPE that makes it transfer to kinetic energy, why does it do this? What is GPE?
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2
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Is the topic of gravitational potential energy convoluted and unnecesary? [closed]
If we throw an object upwards from the surface of the Earth, we do some work on it to give it kinetic energy. Now as it travels up, Gravity of the Earth does negative work on it till it loses all the ...
0
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1
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Why Gravitational Potential is same In Both these cases?
We usually choose Reference point as Infinity which is Linear to the Points
and by this way we gat work done as both force and displacement are in the same direction as well as in the same line which ...
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1
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115
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Why does the calculus derivation for Universal Gravitational Potential Energy not follow calculus laws and become $W=GMm/r$ instead of $W=-GMm/r$? [closed]
So we know that Universal Gravitational Potential Energy is $U=-Gm1m2/r$ where $G$ is the Gravitational Constant and $r$ is the distance between centers of mass. However, the derivation has me ...
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3
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Is it possible to convert gravitational energy directly into electrical energy?
It is possible to produce strong gravitational accelerations on the free electrons of a conductor in order to obtain electrical current. This allows the conversion of gravitational energy directly ...
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128
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Meaning of kinetic energy and non-contact forces
My textbook gives the following physical interpretation for kinetic energy:
The kinetic energy of a particle is equal to the total work that particle can do in the process of being brought to rest.
...
user332598
2
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2
answers
672
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Change in gravitational potential energy when the work is zero
I may be misunderstanding the whole concept , but my doubt is this.
Let us say there is an isolated system comprising of a rock and the Earth. If I was to lift the rock up with a force equal to the ...
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57
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Confusion about an explanation for gravitational's potential energy
So we know that $\Delta U = -W$, where $\Delta U$ is the difference of potential energy and $W$ the work done by the force to move the body from point A to point B.
When analyzing this for the ...
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3
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From where does object gains gravitational potential energy?
If an object is moving upwards with constant velocity in which upward force is supplying energy and gravity is extracting energy till height ($h$), so from where it gained potential energy?
Please ...
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2
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57
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If the change in potential enegry is equal to the negative of the work done, then this principle isn't consistent here in the case freely falling body
Let us assume that a body of mass $m$ falls from height $h_1$ to $h_2$ :
Here the Work done by gravitational force (Conservative force) is :
$$\mathrm{Force \ ×\ Displacement} = mg \ (h_2-h_1) \tag1$$
...
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3
answers
1k
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How is gravitational potential energy $mgh$?
I know the derivation that $W=Fd$, hence $F=mg$ and $d=h$ so energy gained by the body is $mgh$ considering the body on the ground to have $0$ gravitational potential energy.
But the definition of ...
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Will a rocket need the same fuel and energy going 1 g upwards on Earth as a rocket 1 g in space?
Will the gravity of Earth change the result (making the rocket on earth need more fuel and energy than the one in space)? Or it is the same?
user293241
1
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2
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190
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A question on vertical spring mass systems
For a given mass attached to a vertical spring (near the surface of the earth), how do we know that the equilibrium point is halfway between its oscillation? (Let the height at the bottom of ...
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2
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272
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Limitations Of Work-Energy Theorem
Consider the given system which shows a chain $AB$ of length $l$ and the end $A$ is held at rest.
Suppose we release the chain at time $t=0$. How do we find the velocity of the chain when the end $A$ ...
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2
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237
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Total energy of a satellite
I have learnt that change in potential energy in any conservative force field is equal to the negative of work done by that field through a distance. While applying the same for gravitational ...
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2
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88
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How to derive the equation $-G\frac{Mm}{r_1}+G\frac{Mm}{r_2}=\frac{1}{2}mv_1^2-\frac{1}{2}mv^2_2$?
I was just wondering how the following equation is derived:$$-G\frac{Mm}{r_1}+G\frac{Mm}{r_2}=\frac{1}{2}mv_1^2-\frac{1}{2}mv^2_2~?$$
I already understand why the work $W$ done in moving an object ...
- 379
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2
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55
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Energy to counteract gravity without doing work? [duplicate]
Say I wanted to keep a body of 10kg at a certain altitude above the ground. If I elevate it 1m with my own arms or by any other means (with a drone, pulley system...) I'm spending energy in the form ...
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1
answer
2k
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How much vertical weight/height do I need to store 33 kWh of energy? [closed]
My question is the feasibility of a vertical mechanical weight battery, but unlike previous questions, I wanted to give a precise scenario and see if my math is right (which I doubt)
First, it takes 1....
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4
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510
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How work done by a force on a body is negative?
The work done is the product of force acting on a body and the displacement of the body in the direction of the force.
The gravitational potential $\text{energy}=Mgh$ is the negative of the work done ...
0
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2
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420
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How much more net energy do I use walking up hill?
I have a question regarding work done / energy done.
Say a $70\mathrm{kg}$ man walked $100\mathrm{m}$ on a horizontal surface as a constant speed, is it correct to assume the energy done by this man ...
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2
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46
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The effect of potential energy in the absence of conservative force [closed]
Imagine a hypothetical situation, where we throw a ball from the earth's surface and after certain time $t$ the ball's final velocity is equals to 0. And a that instance, gravity doesn't exist (...
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2
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2k
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Work done moving a satellite into higher orbit
I am confused about the concept of work in relation to conservative and non-conservative forces.
When transferring a satellite from a lower orbit into a higher orbit via a Hohmann transfer, my ...
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6
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In the limit, does walking slowly downstairs cost me as much energy as walking upstairs?
I am not a physicist.
If I allow myself to roll down a hill, then apart from receiving bruises, I will expend no energy.
Having suffered ill-health recently, it seemed reasonable for me to restart my ...
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Some questions regarding graviational potential energy and the concept of potential energy in general
Starting off, I first want to know the relation between work and potential energy.
$\Delta\mathbf U = - W $
How was this expression formulated?
Moving on,
My second doubt was in the derivation of the ...
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2
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59
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Does a falling body add energy to the earth?
Gravitational potential energy is inversely proportional to distance:
$$V = G\frac{ m_1 m_2 }{d}.$$ when an asteroid is extremely far from earth, its gravitational potential energy (relative to earth) ...
0
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3
answers
133
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Amount of work: clarifications
If to lift an object of mass $m$ a force greater than $mg$ is required then why do we take the amount of work done in lifting an object as $mgh$ could someone please explain that to me?
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Feynman Lectures Chapter 4.2: Understanding the weight-lifting machine visually
Why a non-reversible weight lifting machine cannot lift higher that a reversible one is related to my current post, but everyone in that thread seems to have understood how Feynman's simple machine ...
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Kinetic energy in "interplanetary" Gravitational potential energy problem?
For a system of two completely stationary planets both of the same radius and mass, when launching a projectile (e.g. a rocket) from point A on the left planet - assuming we know U - minimal kinetic ...
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How to calculate the total energy of a planet at rest?
Let's just say we have the Earth-Moon system isolated in space, with Earth at rest, and the moon orbiting it.
How can we calculate the total energy of Earth in such a case (Kinetic energy would be ...
0
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1
answer
83
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Can gravity be utilized to generate hydropower in a clean, repeatable fashion without rivers or lakes? [closed]
I came up with this idea today and am just wondering if it is feasible. It is much easier to communicate via images so I drew the attached image to convey it. The key concept is rolling a ball in ...
1
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6
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516
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Why work done is needed when other physical quantities are available?
I have some question about work done. I understand the mathematical ways and examples which are floating all over on internet & books. But all these information not clearing the concepts of work ...
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Lagrangian potential for Newtonian gravity
In the Wikipedia site for Lagrangian (field theory) the Lagrangian density for Newtonian gravity is given by
$${\cal L}(\mathbf{x},t) = \frac{1}{2}\rho(\mathbf{x},t)\mathbf{v}^2 -\rho(\mathbf{x},t) \...
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3
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852
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In what direction is positive work done under a gravitational force, and what justifies the relation between work, potential and kinetic energy?
This has confused me for some time: if one integrates the gravitational force between two radii (let the motion of the particle always point toward the centre of mass of the other mass) from a radius ...
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4
answers
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How do you calculate the energy required to hold a weight against gravity?
What is the energy required to hold a mass in place? To lift 1kg 1m at sea level I must use 9.8 J. but if I simply grab onto a 1 kg mass that is on a table and the table is removed. I am now using ...
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