All Questions
15
questions
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76
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Two-body problem and motion in a central field
If we consider motion of a body in a central (gravitational) field the equation of motion would be
$$-\frac{\gamma m_1 m_2}{r^2}\frac{\vec{r}}{r}=m_1 \vec{r}^{\prime\prime}$$
where the origin of ...
- 3
0
votes
2
answers
32
views
Times of free-fall in different inertial reference frames in classical physics
Imagine that a ball is thrown directly down at a rate of 20 m/s from a height of 100m in Earth's gravitational field. If we were to calculate the time it takes to fall we could use the kinematic ...
1
vote
1
answer
378
views
Why do the 2 planets in a two-planet system orbit around the center of mass?
When reading the Feynman Lectures (chapter 7, volume 1), Feynman was explaining the formation of tides on the Earth and said the following:
The moon does not just go around the earth, the earth and ...
- 87
-1
votes
1
answer
63
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In this world of pseudo forces what is real?
I was learning concept of pseudo force and encountered a problem which I found pretty interesting,
I am told that the surface in contact of wedge and box having mass $m$ is frictionless and I am ...
- 11
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votes
1
answer
57
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Are Newton's equations accurate on Earth when we ignore fictitious forces?
I am a high school student and I just got to know about inertial and non-inertial frames of reference. And since the earth is actually accelerating around the sun, and the sun is also accelerating, ...
- 3
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votes
2
answers
96
views
Particle in a gravitational field moving at constant speed in some inertial frame
While working on an unrelated problem I found an interesting result which I presume must already be known, but I cannot find any reference to it. It is the following:
Consider a small particle P ...
- 111
1
vote
1
answer
71
views
Gravitational potential energy with both bodies moving [closed]
When deducing the formula for the gravitational potential energy of one body in relation to the gravitational force of another body, my teacher assumed that one body was standing still. I tried ...
- 13
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votes
1
answer
249
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Motion of bodies released form rest in a freely falling cabin
In a paper I was solving, there was a question stated as such:
A narrow but tall cabin is falling freely near the Earth's surface. Inside the cabin, two small stones A and B are released from rest(...
- 113
1
vote
1
answer
110
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Finding the frame of reference in which Newton's law of gravitation applies
I've always wondered, in which frame of reference does Newton's law
$$
\boldsymbol{g} = -\frac{GM}{r^2} \widehat{\boldsymbol{r}}
$$
actually apply? In general it can't be the one in which the the ...
- 211
3
votes
2
answers
2k
views
Would the Foucault pendulum experiment work on a rotating flat Earth?
If the Earth were to be flat, but still rotating with a constant angular frequency, would the Foucault pendulum still show it's precessing motion?
The angular velocity of the precession can be ...
- 1,438
2
votes
1
answer
330
views
Is an explanation of 'effect of Earth's rotation on $g$' possible from an inertial reference frame?
Edit : Added a picture for better understanding of my querry.
All the texts I have studied has used an non-inertial frame to explain the phenomenon. But every time I see something explained with ...
- 1,228
28
votes
4
answers
7k
views
Are planets actually moving in elliptical orbits around the Sun or do they move in circular orbits around their center of mass?
In every derivation of Kepler's Laws that I have seen, we assume that the sun is stationary. However, in other places I have read that celestial bodies move about their barycentre (center of mass).
So ...
1
vote
3
answers
770
views
Fundamental paradox with Newton's Law of Gravity?
This is my first post here, but I've been struggling with this problem in my head since I studied physics at school when I was 14 (30 years ago!).
There seems to be a fundamental paradox with Newton'...
- 131
3
votes
1
answer
2k
views
Gravity vs inertia
As stated according to Newton laws of gravity, every object with mass attracts all other object with a force which produces acceleration. Basically there are several forces in the universe which ...
- 1,847
0
votes
1
answer
546
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Defining the star as the ellipse focus rather than the barycenter, what does the other focus do? [duplicate]
There are a lot of images and animations on the internet depicting two bodies orbiting around their common barycenter. The barycenter is defined as the (let's say right) focus of the ellipse.
If we ...
- 1,517