All Questions
Tagged with newtonian-gravity energy
125
questions
8
votes
6
answers
16k
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Why is potential energy negative when orbiting in a gravitational field?
I had to do a problem, and part of it was to find the mechanical energy of satellite orbiting around mars, and I had all of the information I needed. I thought the total mechanical energy would be the ...
- 6,235
2
votes
1
answer
75
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Gravitational collapse - proof that energy dissipation is required?
As an undergraduate, I took a short course on astrophysics, where I encountered the Jeans mass. This is the critical mass for a spherical cloud of interstellar gas above which the cloud is predicted ...
- 133k
-1
votes
3
answers
426
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How does gravitational potential energy work in a very large distance?
Consider a thought experiment (that I made when I was in high school) involving a universe with only two objects: a massive planet and a small asteroid. Initially, they are millions of light-years ...
- 109
1
vote
2
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2k
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Angular momentum of the center of mass of yo-yo reaching the end
I am a physics undergrad, and I know only a basic stuff about the subject.
Yesterday, I was taught about the angular momentum of a yo-yo and
my professor said that when the yo-yo hits the end of the ...
- 12.1k
0
votes
1
answer
80
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Where am I wrong in proving that force perpendicular to motion increases speed and kinetic energy? [closed]
Lets think of a helicopter flying at some height $h$. It throws a food packet to a person on the ground from air. Let's neglect the air drag.
The food packet is thrown only with some velocity $v_x$ in ...
- 207k
0
votes
2
answers
420
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How much more net energy do I use walking up hill?
I have a question regarding work done / energy done.
Say a $70\mathrm{kg}$ man walked $100\mathrm{m}$ on a horizontal surface as a constant speed, is it correct to assume the energy done by this man ...
CommunityBot
- 1
0
votes
2
answers
272
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Limitations Of Work-Energy Theorem
Consider the given system which shows a chain $AB$ of length $l$ and the end $A$ is held at rest.
Suppose we release the chain at time $t=0$. How do we find the velocity of the chain when the end $A$ ...
CommunityBot
- 1
2
votes
2
answers
111
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Why do higher objects have a greater force?
We did an experiment in class today using a spring scale, a plastic bag, and a variety of other objects. Essentially, we attached the bag to the spring scale and measured the force, in newtons, of ...
- 133
0
votes
3
answers
7k
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Kinetic energy with no velocity
When a body is displaced against the gravitational field of force it gains potential energy. When we drop the body it begins to move downward with a certain amount of acceleration, and the potential ...
- 436
4
votes
5
answers
4k
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Climbing Stairs and Calories Burnt
I climb stairs to work (20 floors) every day . The least amount of work my body is doing by gaining potential energy (P.E) = mgh where m is mass , g is acc. due to gravity and h is height . Assuming ...
- 1
0
votes
4
answers
510
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How work done by a force on a body is negative?
The work done is the product of force acting on a body and the displacement of the body in the direction of the force.
The gravitational potential $\text{energy}=Mgh$ is the negative of the work done ...
CommunityBot
- 1
1
vote
4
answers
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How do you calculate the energy required to hold a weight against gravity?
What is the energy required to hold a mass in place? To lift 1kg 1m at sea level I must use 9.8 J. but if I simply grab onto a 1 kg mass that is on a table and the table is removed. I am now using ...
- 207k
1
vote
1
answer
336
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How to calculate the energy in a hyperbolic orbit?
I'm recently reading a book about rocket science which involved orbital mechanics. I know that in an elliptical orbit, the energy $ E=-\frac{GMm}{2a}$, and therefore can get the vis-viva equation: $ ...
- 207k
-2
votes
2
answers
159
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Thought experiment: Where does potential energy come from if matter is created from energy?
Let's do a thought experiment:
Assume that I have a machine that can convert energy into matter with 100% efficiency i.e. it can create any amount of matter in a small space so long as I pay it's ...
- 4,487
1
vote
2
answers
301
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Newton's Universal Law of Gravitation doubt
The Universal Law of Gravitation states that the module of the force, $F$ is
$$F = \frac{GmM}{r^2},$$
where $m$ and $M$ are the mass of the two objects and $r$ is the distance between the two objects....
