Questions tagged [energy]
Energy is the conserved quantity associated to time-translation invariance and represents the work a system is capable of doing. Use this tag for questions about energy, and consider adding the [energy-conservation] tag if it is specifically about its conservation.
7,323
questions
1
vote
2
answers
37
views
When a submarine blows its ballast and rises, where did the energy for the ascent come from?
Say a submarine fills it's ballast tanks with water at the surface and in so doing becomes negatively buoyant. It sinks, presumably converting gravitational potential energy into kinetic for the ...
-1
votes
0
answers
9
views
Find the minimum velocity of the disk so that it meets the given conditions? [closed]
Disk and plank of mass M and M/2 respectively, has velocity v, having a plank on top of it, the disk does pure rolling such that the plank on top does not slip. {M= 2kg, R= 2m}
Case:A) Find minimum ...
2
votes
0
answers
43
views
Help with proving the von Roos kinetic energy operator is Hermitian
When calculating the kinetic energy of a variable mass quantum system, such as a semiconductor heterostructure where mass has spatial variance due to the effective mass approximation, von Roos (Phys ...
- 21
0
votes
0
answers
45
views
About $1^{\rm st}$ order phase transitions in Landau theory
Suppose that we have a magnetic system described by the following free energy ($\eta$ being the order parameter, in this case the magnetization)
$$\mathcal{L}(\eta,t,h)=at\eta^{2}-w\eta^{3}+\frac{b}{4}...
- 487
0
votes
0
answers
36
views
Is energy current (or energy flow) conserved if energy is conserved? [closed]
Is energy current (or energy flow) conserved if energy is conserved? Can it be derived from the continuum equation for energy-conservation?
0
votes
0
answers
52
views
What is energy, and why and when is it conserved? [duplicate]
In which field of physics can I find a solution to this question:
What is energy, and why and when is it conserved?
When I asked a similar question to my professors and peers, they said, 'We ...
- 11
0
votes
0
answers
28
views
$\Sigma T.x=0$ in a pulley system as seen from ground [closed]
As we know that if two blockes are connected to a string, wrapped around a pulley then sum of dot product of tension $T$ and acceleration $a$ is zero which comes from the principle that internal ...
- 111
-3
votes
3
answers
77
views
How to convert total solar irradiance from $\rm J m^{-2}h^{-1}$ to $\rm W/m^2$? [closed]
So, I have data of total solar irradiance in Jm^2 units, I'd like to convert it to W/m^2. I googled and found that in order to convert you must divide the initial value by (33600), but even if I do, I ...
-1
votes
0
answers
49
views
Vacuum bubble nucleation by cosmic rays suppressed? [closed]
There are models of vacuum bubble nucleation events that would be cause by high energy density zones like cosmic rays collisions
However, one paper argues that this process is suppressed. I asked the ...
- 2,754
1
vote
5
answers
222
views
What is the potential energy and kinetic energy for capacitor and inductor?
I always thought that $\frac{CU^2}{2}$ is potential energy stored in a capacitor and $\frac{LI^2}{2}$ is kinetic energy stored in inductor. But here and here (page 12) as understand it correctly for ...
- 125
-1
votes
0
answers
58
views
Vacuum energies in different colliding vacuum bubbles?
I got two questions regarding this paper
There, it's analyzed how colliding vacuum bubbles could result in new bubbles and how could this affect their vacuum energy.
Specifically, it considers an ...
- 2,754
0
votes
1
answer
53
views
The kinetic energy of rigid body
I need to determine the kinetic energy of ball rolling with out slipping on a cylinder, and when I searched for it I found that the kinetic energy is:
$$ T = \tfrac12mv^2 + \tfrac12I\omega^2 $$
But ...
2
votes
1
answer
77
views
Minimum work done on a mass to take it along a path [closed]
A particle of mass 1 kg is taken along the path ABCDE from A to E (see figure). The two "hills" are of heights 50m and 100m and the horizontal distance AE is 20m while the path length is ...
3
votes
3
answers
587
views
Energy and force, the basic formula
Energy and force, the basic formula
Can someone explain to me this chain of equalities?
Namely the $v$ in the 4th term and the next term: $$\int d/dt \ ((m/2) v^2) \ dt$$
$$E = \int F \ ds = \int m a \...
- 31
0
votes
2
answers
49
views
Acceleration in spring-mass system [closed]
So the original question is to find the maximum elongation in the spring:
https://imgur.com/a/hI4o3HH
The solution used $F_{net}=ma$ for both the masses.But,they assumed same acceleration for both of ...
- 301