All Questions
87
questions
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How much time does it take for an object to fall from space? [closed]
Let's say there's an object of mass $m$ in space, $h$ meters away from the surface of the Earth. $h$ is large enough that $g$ cannot be assumed to be constant. The acceleration varies according to ...
- 117
1
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1
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89
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How does gravity act and propagate in a 2+1D universe?—Newtonian versus general relativity
In a hypothetical 2+1D universe:
if we apply the Newtonian concept of gravity, we might expect that the gravitational force between two mass points with a distance of $r$ would diminish linearly with ...
- 618
0
votes
2
answers
33
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Understanding conservation of angular momentum in relation with rotating objects
Conservation of angular momentum says that the angular momentum of a closed system will not change if there is no external torque applied to the system. For example, let's take the example of a ...
- 665
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2
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180
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How much kinetic energy would a star in a galaxy have if it fell to the center?
I want to calculate the speed, or equivalently, the kinetic energy of a star, if it had no rotational speed and fell from a given radius to the center of the galaxy.
I assume Newton's shell theorem ...
- 476
1
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1
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29
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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 ...
- 13
0
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1
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39
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How a force that is always perpendicular to velocity can change the kinetic energy when another force is acting oppposite to velocity? [closed]
When a satellite is revolving around a planet with an orbital velocity in presence of air resistance, the satellite's Kinetic Energy keeps on increasing as it falls down. The resistive force is trying ...
- 101
2
votes
1
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267
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How to calculate the period of non-circular orbits?
How to calculate the period of non-circular orbits?
By conservation of mechanical energy:
$$
E = -\frac{GMm}{r} + \frac{1}{2}\mu \left ( \dot{r}^2 + r^2 \dot{\theta}^2 \right )
$$
By the conservation ...
- 1,525
1
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3
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140
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Do objects with non-uniform shapes and mass distributions rotate as a result of gravitational attraction?
I was thinking about orbital mechanics this morning and a question arose: do objects with non-uniform shapes and mass distributions rotate as a result of gravitational attraction?
Thinking through the ...
- 822
-2
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1
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328
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Do black holes exert infinite forces?
Black holes have infinite mass so according to Newton's law of universal gravitation should exert and infinite amount of gravity force.
- 90
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1
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261
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Gravity Differential Equations
I was just messing around with Newton's Law of gravitation, when I had the idea of converting Newton's Law into differential form (more or less like Maxwell's equations).
I did the following:
#1 ...
- 1,525
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3
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74
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How velocity affects different orbits?
Assume a sun with mass $M$ and a planet with mass $m$. Assume at $t_0$ the planet is $r_0$ (distance) away from sun and has an initial velocity of $v_0$. Also, let’s assume the angle between the $r_0$ ...
- 117
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3
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95
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How can weight be equal in the equivalence principle?
According to Einstein, weight will be the same as here in earth in a rocket going at 1G far from gravity fields. If we propulse an object here it will feel two forces, F=mg and F=ma of the thrust, but ...
user189508
0
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0
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60
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What is the gravitational force of a intangible sphere inside another sphere?
This is similar to the problem of the gravitational force of a particle inside a sphere, but instead of a particle, I want to know how two objects of non-negligible size and mass would interact ...
1
vote
1
answer
62
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What will be the tension force in this case?
Suppose I have a block of mass $2\, {\rm kg}$ sitting on my table. Then I connect a string to it and pull it vertically upwards. The resultant acceleration is vertically upwards: $2.2\, {\rm ms}^{-2}$....
- 1,018
1
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136
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Conceptual Question: What would happen to satellites orbiting the earth if mass of earth suddenly increases? [closed]
Would the satellite crash onto the earth? If so, why, and in what kind of motion? A spiral motion sounds intuitive, but why?
Or there is another possibility: will the satellite continue to execute ...
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