All Questions
13
questions
1
vote
3
answers
75
views
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
2
votes
1
answer
267
views
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
0
votes
6
answers
95
views
Free falling bodies in the absence of external forces
We know that if two balls $B_{1}$ and $B_{2}$ having masses $m_{1}$ and $m_{2}$ respectively and suppose $m_{1}$ is sufficient greater than $m_{2}$. In daily life observation, we see that both the ...
- 27
0
votes
1
answer
648
views
Newton's first law - elevator lift upward and downward force [duplicate]
Why does $F_c$ is equal to $F_g$ and why $F_c$ isn't greater than $F_g$? $F_c$ is moving it upward right, so the force must be greater than gravity to pull it upwards I think.
- 101
1
vote
1
answer
58
views
Justification for the nature of planet's orbit in gravitational field!
In kleppner Mechanics in the chapter central force he derived the polar form of orbit for gravitational force as illustrated below: (first two equations are derived from fundamentals of central force)
...
0
votes
1
answer
296
views
Path of an object in gravitational field [duplicate]
How do you prove that path of a satellite or a planet is a second degree curve? In other words, how do you prove Kepler's law which states that planets move in elliptical paths?
0
votes
1
answer
240
views
Toppling over of a body
Why does a body topple over only when the perpendicular from its centre of gravity does not pass through its base?
I had read a paragraph on it from a book by Y. Perelman. I did find a half-...
- 496
0
votes
1
answer
2k
views
Distance between centre of earth and centre of moon
So here's the question:
Calculate the approximate distance between the centre of the Earth and the centre of
the moon. You may use the mass of the Earth as $6\times10^{24} kg$ and $G = 6.67\times10^{-...
1
vote
2
answers
120
views
Need proper interpretation of imploding/exploding self-gravitating sphere
While searching for some nice and simple problems in Newton's theory of gravity, I've made this trivial calculation for which a proper physical interpretation is lacking. Some pieces are missing and ...
- 7,592
88
votes
8
answers
10k
views
Could a "living planet" alter its own trajectory only by changing its shape?
In Stanislaw Lem's novel Solaris the planet is able to correct its own trajectory by some unspecified means. Assuming its momentum and angular momentum is conserved (it doesn't eject or absorb any ...
- 3,109
2
votes
0
answers
41
views
Marvin the Martian vs. the Death Star: how much energy will they actually need to disintegrate the Earth? [duplicate]
Marvin the Martian vs. the Death Star: how much energy will they actually need to disintegrate the Earth?
According to a detailed analysis by Dave Typinski, Marvin the Martian’s Illudium Q-36 ...
- 360
9
votes
1
answer
614
views
Marvin the Martian vs. the Death Star: how much energy will they actually need to disintegrate the Earth?
According to a detailed analysis by Dave Typinski, Marvin the Martian’s Illudium Q-36 Explosive Space Modulator will require $1.711 \cdot 10^{32}~\text{J}$ to shatter the Earth into a gravitationally ...
- 360
1
vote
4
answers
225
views
Gravity and acceleration
I've imagined this little scenario to help me conceptualize things.
Let's say we have a doughnut-shaped object with a hole whose diameter is greater than that of a sphere. Let's say that the sphere ...
- 221