All Questions
55
questions
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2
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153
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Does work increases as accelaration increases?
If work is a product of force and displacement, and force increases as acceleration increases, does these mean that work is dependent on acceleration? For instance, if I lift a block faster, does this ...
5
votes
4
answers
2k
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Work done by constraint forces -- Generalisation
Consider the above scenario: In the subsequent motion, we need to find the work done by tension on the (trolley + mass) system.
Solution: Suppose at an instant, the velocity of the trolley (and hence ...
- 1,295
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1
answer
133
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The "coefficients" of virtual displacement in Goldstein's classical mechanics
In Goldstein's classical mechanics the following passage is confusing me:
We therefore have as the condition for equilibrium of a system that the virtual work of the applied forces vanishes: $$\sum_i ...
- 6,963
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votes
2
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459
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Path independence of a conservative force
My book Halliday et al. gives a proof of the path independence (conservative force). It is said that the net work to move a particle from a to b and then from b to a is zero. Thus the work done from a ...
user248666
2
votes
3
answers
720
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Work done by tension on a system-generalisation
In All the Classical Mechanics problems I have come across so far, There's one thing that happens invariably: That the work done by tension is zero. Mostly, It simply happens because the (massless) ...
- 1,295
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2
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615
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Work done by friction over closed path
I am stuck thinking about work done by non-conservative forces. It is path dependent.
Let us consider an example.
A truck starts from rest and a block is kept on it. It accelerates for some time and ...
- 125
2
votes
1
answer
143
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Example of a single constraint force doing virtual work despite the sum of work done by constraints being zero
When deriving d'Alembert's Principle it must be assumed, that the total virtual work done by constraint forces vanishes.
$$\sum_{j=1}^N\mathbf{C}_j\cdot\delta \mathbf{r}_j=0.$$
In the books I've read, ...
- 72
1
vote
2
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144
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Work done as change of potential, how total derivative is converted to partial derivative
I am reading Goldsetein's Classic Mechanics 3rd edition in Chapter 1 it says,
If work done in moving form point 1 to 2 denoted by $W_{12}$, is independent of the path it should be possible to ...
- 113
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votes
2
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192
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In order for a force to be derived from the gradient of a potential energy, does the work done by such a force need to be invariant of the path?
Suppose a force $\mathbf{F} = \mathbf{F}(\mathbf{r}, t)$ where $\mathbf{r}$ is a three dimensional space vector and $t$ is time.
I understand that in order to a force be conservative two conditions ...
- 376
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1
answer
104
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Equation for total work for a system of particles, modeled as a single particle, acted upon by multiple variable forces in three dimensions?
I am attempting to generalize the equation for the total work done by multiple, constant forces on a system that can be modeled as a single particle (that is, a system that moves so that all the parts ...
- 125
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4
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2k
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Why the total virtual work done by forces from constraints vanishes? (Perpendicularity of two or more particles)
My mechanics book claims that the total force on the $i$-th particle is
$$
F_i=K_i+Z_i \tag{2.5}
$$where $Z_i$ is the force due to constraints and $K_i$ the real, dynamic force. Then, the book states ...
- 1,335
2
votes
1
answer
2k
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Is total mechanical energy always equal to maximum potential energy?
Am I correct in stating this: When initial velocity of an object is $0$ then the total mechanical energy will always be equal to the maximum potential energy (with maximum height or displacement) (...
- 23
1
vote
2
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10k
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Work done by a person climbing stairs, who or what does the work? [duplicate]
I've seen other questions like this but didn't really see any answers.
When a person climbs stairs, the object is the person. Yet we say the person did work...how so? Doesn't work mean an external ...
- 379
3
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1
answer
358
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Conservative field vs conservative force
For a conservative field (e.g. electrostatic field) the circulation of the field (along a closed line) is zero.
For a conservative force (e.g. macroscopic elastic force) the work performed on a ...
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1
answer
125
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Force Applied but No Distance Travelled
Suppose I push on a wall with a constant force of 5 N for 10 s. The wall won't move and hence no work will be done on the wall. However, pushing requires energy. How can I find out how much energy I ...
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