All Questions
38
questions
0
votes
1
answer
36
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Drawbacks of Quasi-Static process for lifting a block
Definition of Quasi-static: A quasi-static process is a thermodynamic or mechanical process that occurs very slowly, allowing the system to remain in a state of equilibrium at all times.
While ...
- 21
0
votes
1
answer
58
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Question about Problem $12$ in Chapter $11$ from Kibble & Berkshire's book
I write again the problem for convinience:
A rigid rod of length $2a$ is suspended by two light, inextensible strings of length $l$ joining its ends to supports also a distance $2a$ apart and level ...
0
votes
2
answers
74
views
Energy in different coordinates in central force motion
With reference to central force, we see that K.E has 2 terms in 2D cartesian cordinate but just 1 term in polar coordinates and potential energy has 1 term in cartesian but 2 terms in polar.
Basically ...
- 367
0
votes
2
answers
82
views
Does mechanical energy means total energy?
I know that mechanical energy is the sum of kinetic energy and potential energy. But there is a sentence in the book like this:
'Our primary goal, however, is to find the energies associated with ...
- 107
0
votes
6
answers
287
views
Does potential energy actually exist? Or is it just a useful mathematical model? [closed]
The title basically covers it. I've actually thought about this question for a while now, and I am still not sure if I have a definitive answer. Most potential energies seem to just be the work that ...
- 183
0
votes
2
answers
44
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Potential energy separately for each object
Potential energy change is :
$\Delta U = -W_{int}$ where $W_{int}$ is the internal forces.
For the ball which is falling down towards earth, we can write:
$\Delta U = -(W_{earth} + W_{ball}) = -(K_{...
- 137
1
vote
4
answers
204
views
Circular reasoning involving conservation of energy and the definition of potential energy? [closed]
This might seem a dumb question but it is at the heart of mechanics.
We learn that in our universe the total energy of a closed physical system is conserved, never destroyed, never created, only ...
- 2,987
0
votes
3
answers
88
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Consolidating two ways to calculate work
I was wondering if I could get some help closing some fundamental gaps in my intuition of work, as it relates to force and distance travelled.
Scenario
Say we pull a 1kg box along the ground. We pull ...
- 163
1
vote
1
answer
91
views
Kinetic and Potential Energy of a multi degree of freedom (MDOF) system
Consider the following MDOF system:
$M\ddot x+Kx=F$
where $M$ and $K$ are the mass and stiffness matrix respectively, and $x$ and $F$ are the displacement and force vectors.
How can one determine the ...
- 15
0
votes
5
answers
97
views
How can potential energy increase? [closed]
If work is done on a body, the energy of the body increases. If work is done by the body, energy decreases. When we take a body up to some height, some work is done by us on the body, which is stored ...
1
vote
3
answers
620
views
If energy is a scalar quantity, how can it be negative?
We are studying electrical potential energy in my high school class. I was originally taught that energy is a scalar identity, but the electrical field equation says that there can be negative ...
- 139
0
votes
2
answers
810
views
Classical analog of the statement "$E$ must exceed the minimum value of $V(x)$
Overall question:
Griffiths problem 2.2 states that $E$ must exceed the minimum value of $V(x)$ for every normalizable solution to the time-independent Schrodinger equation. Then, it asks for a proof ...
- 1,261
0
votes
0
answers
689
views
Lagrangian intuition [duplicate]
I am new to lagrangian mechanics and it just baffles me the idea of subtracting potential energy from kinetic energy. Why don't we use kinetic energy alone and the least action path (between two ...
- 105
0
votes
2
answers
57
views
If the change in potential enegry is equal to the negative of the work done, then this principle isn't consistent here in the case freely falling body
Let us assume that a body of mass $m$ falls from height $h_1$ to $h_2$ :
Here the Work done by gravitational force (Conservative force) is :
$$\mathrm{Force \ ×\ Displacement} = mg \ (h_2-h_1) \tag1$$
...
1
vote
0
answers
98
views
How to find energy for bounded orbit?
I have a time-independent Hamiltonian which describes a system. How do I find the energy threshold where the orbit stops being bounded? That is when there does not exists no zero-velocity surface?
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