All Questions
65
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Gravitational potential in a system of two particles
Suppose two particles with masses $m_1$ and $m_2$ are interacting via a central force. Lets work in the center-of-mass frame, and let $r$ be the distance from the masses to the center of mass which ...
- 273
1
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2
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678
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How do we find the average value of gravitational potential energy over one orbit?
We just completed orbital dynamics in my university astrophysics class. The textbook we are using is Carroll and Ostlie. In the textbook, it is mentioned that the average gravitational potential ...
1
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2
answers
143
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Part of physics answer I didn't understand, and don't have reputation to ask them. $10\,\text{ms}^{−2}$
When you lift your $2.5 \,\text{kg}$ laptop (a 15-inch Apple MacBook Pro, for example) by a foot, you do work of approximately $2.5 \,\text{kg} \times 10 \,\text{ms}^{−2} \times 0.3 \,\text{m} = 7.5 \,...
1
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1
answer
70
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My question is regarding gravitational potential [closed]
If you take a spherical shell, say of mass $M$, and then you split the shell in 2 portions by a plane other than the median plane....say that the larger portion is A and the smaller portion is B.......
1
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1
answer
2k
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Gravitational potential at the centre of Earth [duplicate]
Why does gravitational potential at the centre of the Earth is finite i.e. $V_c=\frac{3}{2} V_s$, as at the centre $r$ becomes zero so applying $V = \frac{GM}{r}$ the result must be infinity.
- 149
1
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1
answer
395
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The amount of work needed to dig a hole in the ground [closed]
I'm trying to calculate the amount of work that is needed to dig a hole in the ground (can be very deep) between the surface of the Earth with radius $R_{Earth}$ and some surface with radius $R$. As ...
- 11
2
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2
answers
1k
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Trying to figure out the potential energy of a hanging rope [closed]
I was trying to figure out the potential energy of a hanging rope. The rope is hanging from a fixed support. The mass of the rope is $m$. And the length of the rope is $\ell$. The rope has a uniform ...
- 529
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2
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79
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Problem involving gravitational potential energy [closed]
Two uniform solid spheres of equal radii $R$, but mass $M$ and $4M$ have a centre separation of $6R$. The two spheres are held fixed. A projectile of mass $m$ is projected from the surface of the ...
-1
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3
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1k
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Derive gravitational potential energy for this system [closed]
This is on a study guide for my Physics 221 final. I feel like I almost got it but I am off by a sign error. Here is the question:
Here is what I got so far:
Known:
$$F_g = \frac{GMm}{r^2}$$
$$U_g =...
- 101
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votes
1
answer
33
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How much energy will be created using this method? [closed]
If I built a platform 100 meters high and put a crane on it then used solar power grid to drive the crane motor. Then using a 40 foot shipping container l filled it with dried sand. Then using the ...
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2
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51
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Simplified formula of potential energy giving different expected value of mass
I am trying to calculate the mass of a planet by the following image
I have the mass of the object, $2$ kg, and the radius of the planet, $5000$ km (also the gravitational constant $G$).
My first ...
- 105
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votes
1
answer
45
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Potential energy of an object (with non-negligible size compared to distance from ground level)
Let's say I have a cylindrical water tank (with area $A$ and height $h$), and the bottom of the tank is $H$ meter from the ground.
So what is the potential energy of the water tank? If the $h$ is ...
- 2,566
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votes
1
answer
459
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Gravitational potential energy of an isothermal sphere
I am trying to calculate the gravitational potential energy, W, defined as:
$$W = -\frac{1}{2}\int\rho(r)\Phi(r)\mathrm d^{3}r$$
for an isothermal sphere. I am given that the density profile varies ...
- 71
2
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0
answers
710
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Gravitational potential of an infinite plane
In this link http://www.feynmanlectures.caltech.edu/I_13.html#Ch13-S4 , Feynman first computes the gravitational field generated by an infinite plane of constant density, and then he computes the ...
- 592
3
votes
4
answers
712
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Rocket Leaving Earth's Gravitational Field
I stumbled across this seemingly simple question that really stumped me on further thought:
A rocket is intended to leave the Earth's gravitational field. The fuel in its main engine is a little ...
