The Newtonian model of gravity in which the force between two objects is given by GMm/r^2.
0
votes
1answer
125 views
Vertical Loop like Anti-gravity
Let's take a bottle (no cap) with half its volume filled with water. If we rotate the bottle at some slower average velocity, water does not drop out of it. The same principle works on Roller ...
0
votes
2answers
770 views
Physics behind Water drops during falling from a tap
what is physics behind Water drops during falling from a tap.
water drop animation
A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces.
Why Water ...
1
vote
1answer
96 views
Gravitation and equilibrium (…and similar problems)
One problem that I'm having trouble with (as opposed to the other):
The Messenger is a probe that orbits Mercury $700 \rm km$ from the surface. What is the tangential velocity it should be ...
-1
votes
4answers
203 views
How to send a spacecraft to the moon without any acceleration
I have two (maybe equal) question
1- Is this possible to send a spacecraft to the moon without any acceleration(Constant speed)?
2-Is this possible to throw a ball on the top of tree without any ...
5
votes
4answers
2k views
The Time That 2 Masses Will Collide Due To Newtonian Gravity
My friend and I have been wracking our heads with this one for the past 3 hours...
We have 2 point masses, $m$ and $M$ in a perfect world separated by radius r. Starting from rest, they both begin to ...
0
votes
1answer
190 views
Time taken for object in space to fall to earth
The Problem
For a small mass a distance $R_i$ away from the center of the Earth, how long would it take for the object to fall to the surface of the Earth, assuming that the only force acting upon the ...
6
votes
10answers
959 views
Is the distance between the sun and the earth increasing?
M = mass of the sun
m = mass of the earth
r = distance between the earth and the sun
The sun is converting mass into energy by nuclear fusion.
$F = \frac{GMm}{r^2} = \frac{mv^2}{r} \rightarrow r ...
9
votes
3answers
1k views
Why does the moon drift away from earth?
I once saw on TV that the moon is slowly drifting away from the earth, something like an inch a year. In relation to that the day on earth what also increase in time.
I wonder why is that?
2
votes
1answer
160 views
Would the Moon drift away from the Earth due to extraction of tidal energy? [duplicate]
Possible Duplicate:
Why does the moon drift away from earth?
It seems to me that, due to conservation of energy, the moon would drift away from the Earth if humans began extracting large ...
0
votes
1answer
128 views
why does gravitational force bring the clouds down? [duplicate]
Possible Duplicate:
The Density of Clouds
according to definition of cloud :
A visible mass of condensed water vapor floating in the atmosphere, typically high above the ground
as there's ...
2
votes
1answer
164 views
Do Lagrangian points actually maintain a fixed distance?
I was reading on up Lagrangian points and the restricted three-body problem.
From what I was able to tell, the Lagrangian points are 5 points in a two-body system such that a third body would be ...
1
vote
3answers
93 views
How can one know if a theory allow action at a distance effects or not?
1-In general, if a theory has action at a distance effects, where can that appear exactly in the theory?
2-Does it appear in the dynamical law of the theory? (does it appear in Newton's 2nd law? ...
0
votes
2answers
179 views
Hanging a Hammock
I have a hammock that I want to hang using a tree on one end and a wooden post set in a bucket of cement on the other end.
How would I determine how heavy the cement needs to be so that it would ...
0
votes
4answers
541 views
Questions from elevator ride
I like to play inside the lift (elevator). For instance, there are bars attached at the side of the lift, and I like to hold my body up using my two hands on the bar. I realised that I actually feel ...
3
votes
1answer
294 views
Change in appearance of liquid drop due to gravity
A liquid drop is spherical in shape due to surface tension. But why does it appear as a vertical line under the free-fall due to gravity? (E.g. During a rain - falling raindrop) Is there a specified ...
1
vote
1answer
146 views
How do I factor in multiple forces into these Newtonian mechanics equations?
Say a person is walking along.
He then jumps.
The person weighs $25$kg (irrelevant?).
Just after jumping, his velocity is 5m/s (positive is taken as up).
Gravity is taken as ...
3
votes
5answers
363 views
Does Newtonian mechanics predict the bending of the course of light by objects with mass?
$F=Gm_1m_2/d^2$
$F=ma$
$a_g=Gm_{other}/d^2$
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 the ...
2
votes
5answers
974 views
Why Gravity attracts all objects with the same speed?
Why Gravity attracts all objects with the same speed? Is this question was solved? What is the exact answer?
9
votes
3answers
429 views
How do we explain accelerated motion in Newtonian physics and in modern physics?
Maybe my question will seem stupid, but I am not a physicist so I have some problems understanding a classic Newtonian experiment: in the bucket experiment, why does he have to introduce the absolute ...
2
votes
1answer
136 views
Newton's law of gravitation in complex form
In an ebook about elementary complex analysis I came across Newton's law of universal gravitation with a complex valued function in place of $r(t)$. Can somebody please explain the intuition about how ...
6
votes
1answer
426 views
The gravitational potential of ellipsoid
In the literature (Kirchhoff G. - Mechanic (1897), Lecture 18 or Lamb, H. - Hydrodynamics (1879)) one can find the following analytical closed form expression for the gravitational potential of ...
2
votes
2answers
219 views
The shape of the earth$\ldots$
....is an oblate spheroid because centrifugal force stretches the tropical regions to a point farther from the center than they would be if the planet did not rotate. So we all learned in childhood, ...
0
votes
0answers
68 views
Trajectory of a photon due to a constant/uniform gravitational force [closed]
I have a small problem of physics linked to a basic ray tracing algorithm. My problem is the following :
At $t = 0$, a photon at the position $(x_0 = x_\text{min},y_0 = y_\text{min})$ with the ...
1
vote
1answer
71 views
What's the amount of deviation of cellestial orbits from perfect ellipses
It's well known that the planets don't orbit the sun in perfect circles and the characteristics of the elliptical orbits which serve as better approximations to their motion have been calculated ...
2
votes
1answer
147 views
Does a slinky hanging downward double in length if gravity doubles?
Also would a spring under tension greater than the force of gravity pulling the spring downward shrink in both directions until it has depleted it's stored energy while in free fall?
5
votes
1answer
317 views
Kepler problem in time: how do two gravitationally attracting particles move?
Two particles with initial positions and velocities $r_1,v_1$ and $r_2,v_2$ are interacting by the inverse square law (with G=1), so that
$$ {d^2r_1\over dt^2} = - { m_2(r_1-r_2)\over |r_1-r_2|^3} $$
...
0
votes
1answer
343 views
How calculate the angle to launch an object at the maximum distance?
Suppose that you want to launch an object that travels the longest distance, given the starting speed (or the force applied). You have to determine the angle that al you to reach the longest distance, ...
2
votes
2answers
796 views
How gravitation effect on tides
I know that tide is caused by the gravitational pull of moon but what I don't know is how it effects on water. I have actually these doubts.
Why does gravity of the moon creates tides only in water?
...
2
votes
1answer
74 views
How should I be thinking about tides?
I am working on a project for physics that involves tides. This is my current mind set when thinking about tides:
The earth applies a gravitational force on some mass ...
9
votes
1answer
273 views
Apollo and orbital mechanics: orbital decay if the Trans Earth Injection (TEI) burn had failed
I'm reading Jim Lovell (Apollo 8 and 13) and Jeffrey Kluger's book Apollo 13, which is a fantastic read about a long past era I only have kindergarten memories of. On page 54 there is a paragraph that ...
2
votes
2answers
139 views
Were there any efforts made by early physicists to discover and explain how composite bodies fall?
At the dawn of the modern era, Galileo discovered and described how composite bodies fall through the air (or at least the discovery is usually attributed to him).
I'm interested in whether this had ...
0
votes
2answers
164 views
Dynamics - Beginner question
I am trying to understand this question, but I keep coming to a dead end:
Two identical rectangular masses rest on top of one another, the top is tied to a wall on the left, while the one on the ...
0
votes
1answer
60 views
Would we feel the rotation of a rotating habitat?
Assume that a space habitat is shaped like a can with the "top" open.
lets say we attach the can's top to a string with an astronaut standing on the base. We then rotate the can in deep space using ...
2
votes
2answers
462 views
How do you weigh a box on a scale whose limit is too low?
As you will see I know nothing about physics and after being asked to solve a physics problem in a recent interview wanted to ask it of professionals and see what the response would be:
I have a set ...
1
vote
1answer
139 views
Accelerating elevator?
If your in an elevator accelerating downwards faster than gravity, would you be pushed up to the ceiling? Since gravity cannot match the acceleration of the elevator, you're wouldn't be able to move ...
0
votes
1answer
108 views
What would be the path of the earth seen by the astronaut in the lunar sky? [closed]
An astronaut camps on the moon for a period of one month as per the earth’s calendar.
What would be the path of the earth seen by the astronaut in the lunar sky?
(A) The earth remains approximately ...
8
votes
1answer
1k views
What is the maximum efficiency of a trebuchet?
Using purely gravitational potential energy, what is the highest efficiency one can achieve with a trebuchet counter-weight type of machine? Efficiency defined here as transformation of potential ...
0
votes
3answers
1k views
Centripetal/Gravitational Force
Suppose a satellite is orbiting the Earth. The gravitational and centripetal force supposedly point towards the Earth. Therefore, the net force is towards the Earth. Since the satellite doesn't fall ...
1
vote
0answers
367 views
Calculating semi-major axis of binary stars from velocity, position and mass
I'm trying to calculate the 'instantaneous' semi-major axis of a binary system with two equal (known) mass stars for an $N$-body simulation. I know their velocities and positions at a given time, but ...
3
votes
1answer
384 views
Gravitational attraction of triangles
Suppose I have two triangles relatively close together (so they probably shouldn't really be treated as point masses). I want to calculate the gravitational force (and potentially torque?) generated ...
4
votes
5answers
396 views
Gravitation in a space that is topologically toroidal
In my scant spare time I'm building an Asteroids game. You know - a little ship equipped with a pea shooter and a bunch of asteroids floating around everywhere waiting to be to blown up. But, I wanted ...
-4
votes
2answers
142 views
Gravitational attraction [closed]
The mutual force with gravitational attraction between two masses is 500N.
a. If the masses are moved 5 times as far apart, what is the new mutual force of gravitational attraction?
b. If the masses ...
2
votes
2answers
119 views
How does gravity behave outside the geoid?
I was watching a program about the geoid recently and the relative "height" of the Himalayan plateau gave me an idea. It makes sense for the geoid to be "highest" (is that the correct term?) there as ...
1
vote
3answers
297 views
Numerical simulation of mechanics problem
Say I have a planet and shoot something with a given velocity, which is a significant portion of the escape velocity, in a given angle into the sky. It has some initial velocity and there is the force ...
0
votes
3answers
553 views
Still trying to understand gravitational potential and Poisson's equation?
A week or so back I asked a question about the gravitational potential field
$$\phi=\frac{-Gm}{r}, \qquad r\neq 0, $$
and how to show the Laplacian of $\phi$ equals zero for $r\neq 0$? Eventually, ...
1
vote
2answers
160 views
Why no basis vector in Newtonian gravitational vector field?
In my textbook, the gravitational field is given by$$\mathbf{g}\left(\mathbf{r}\right)=-G\frac{M}{\left|\mathbf{r}\right|^{2}}e_{r}$$
which is a vector field. On the same page, it is also given as a ...
3
votes
1answer
408 views
Trying to understand Laplace's equation
I'm struggling here so please excuse if I'm writing nonsense.
I understand that the gravitational potential field, a scalar field, is given by $$\phi=\frac{-Gm}{r}$$
where $\phi$
is the ...
0
votes
1answer
110 views
How to find the orbit of a moving point object given 3 past passing positions?
How do I find the orbit of a moving point object given 3 past passing positions and the tangents at these passing positions, and given that the orbit is known to be an ellipse?
6
votes
4answers
617 views
Can gravity be shielded, like electromagnetism?
If I remember well, they said that it can't, but I do not know why.
Yes, I meant if gravity can be shielded using something like a Faraday cage
(or something else?).
Thank you.
2
votes
1answer
571 views
Simulating Gravity in 3D Game?
Alright, I am writing a space simulator for a 3D game and I would like to implement gravity of objects into it.
Is there a nice way to find a velocity vector which can be added to my engine output ...
