All Questions
Tagged with classical-mechanics work
38
questions
7
votes
1
answer
2k
views
A Question about Virtual Work related to Newton's Third Law
In describing d'Alembert's principle, the lecture note I was provided with states that the total force $\mathbb F_l$ acting on a particle can be taken as,
$$\mathbb F_l=F_l+\sum_mf_{ml}+C_l,$$
where $...
- 190
52
votes
4
answers
12k
views
What's the real fundamental definition of energy?
Some physical quantities like position, velocity, momentum and force, have precise definition even on basic textbooks, however energy is a little confusing for me. My point here is: using our ...
- 36.4k
12
votes
2
answers
7k
views
Can a force in an explicitly time dependent classical system be conservative?
If I consider equations of motion derived from the principle of least action for an explicitly time dependent Lagrangian
$$\delta S[L[q(\text{t}),q'(\text{t}),{\bf t}]]=0,$$
under what circumstances (...
- 8,513
4
votes
2
answers
598
views
Work done changes between reference frames?
(This is not homework; a friend shared with me this puzzler and neither of us can figure it out.) Suppose you are in a plane traveling at velocity $v_1$ relative to the ground. The flight attendent ...
- 43
18
votes
2
answers
107k
views
Conceptually, what is negative work?
I'm having some trouble understanding the concept of negative work. For example, my book says that if I lower a box to the ground, the box does positive work on my hands and my hands do negative work ...
- 181
14
votes
5
answers
49k
views
Proof of conservation of energy?
How is it proved to be always true? It's a fundamental principle in Physics based on all of our currents observations of multiple systems in the universe. Is it always true to all systems? Because we ...
- 677
2
votes
1
answer
466
views
How can I understand work conceptually?
I'm in a mechanical physics class, and I'm having a hard time understanding what the quantity of work represents. How can I understand it conceptually?
- 135
20
votes
3
answers
4k
views
Conditions for a force to be conservative
Taylor's classical mechanics ,chapter 4, states:
A force is conservative,if and only if it satisfies two conditions:
$\vec{F}$ is a function of only the position. i.e $\vec{F}=\vec{F}(\vec{r})$.
The ...
- 1,295
2
votes
2
answers
772
views
How does the work-energy theorem relate to the first law of thermodynamics?
The work energy theorem states that the net work on a particle is equal to the change in the kinetic energy of the particle:
$$W_{net}=\Delta K $$
My first question is whether this formula (the work-...
- 1,581
1
vote
3
answers
593
views
What is the correct way to estimate the work done by a climber?
My teacher gave us a worksheet with word problems and their solutions. It is in German, so I have tried my best to translate it to English:
A 26 year old man climbs Mount Everest (8848 m) in only 8 ...
- 19
1
vote
3
answers
9k
views
Why can't we define a potential energy for a non-conservative force? [closed]
We could define potential energies for non-conservative forces too and then we could conserve it with kinetic and potential energy as we know it. But no one does that. Why is this? Please explain. Any ...
- 903
5
votes
2
answers
2k
views
Why does the work-energy theorem need to include internal forces?
Can anyone kindly explain me why work energy theorem must also include internal forces?
The proof of work energy theorem is derived from Newton's laws of motion, but Newton's laws of motion don't ...
- 399
4
votes
6
answers
1k
views
Does work-energy theorem account for thermal energy?
Suppose a box (which I assume to be a rigid body) with an initial velocity that starts to slide on a level surface with friction. Imagine this experiment is done in vacuum, so there is no air drag or ...
- 61
3
votes
3
answers
4k
views
What is the work done against a force?
Suppose a particle travels a path $\gamma : I\subset \mathbb{R}\to \mathbb{R}^3$ subject to a force $\mathbf{F}: \mathbb{R}^3\to T\mathbb{R}^3$, then we know that we define the work done by the force ...
- 36.4k
3
votes
3
answers
223
views
Where does a torque-invoking force belong in work energy theorem?
First of all, sorry for the poorly phrased question, simply couldn't figure out a better way to put it.
So, the work energy theorem states that work done on an object is equal to the change in its ...
- 368