All Questions
7
questions
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Why is $f = -\frac{du}{dx}$?
I am studying Newtonian Mechanics and I am familiar with single variable calculus.
I came across the concept of conservative and non conservative forces and potential energy. Here is what I understand:...
1
vote
1
answer
146
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How to choose the sign of the differential?
I know this is a very simple question, and I have searched it too. How to avoid incorrect symbols in calculation results.I don’t understand how to choose the sign of $ds$.
An object moves from a to b,...
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34
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5
answers
65k
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Why is the potential energy equal to the negative integral of a force?
Why is the potential energy equals to the negative integral of a force? I am really confused with this negative sign. For example, why there is a negative sign in the gravitational potential energy ...
- 736
4
votes
5
answers
25k
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How can you tell if the work done by a force is negative?
This is kind of confusing to me. I'm guessing that it's specific to the problem. Is the work done by friction always negative? Is the work done by gravity always negative? Spring as well?
It seems ...
- 329
0
votes
1
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268
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Integral limits when calculating the work
If I integrate
$$dW= \vec{ F} \cdot d\vec{\ell}$$
which are the limits?
In
$$\int\limits_{W_{inf}}^{W_{sup}}dW= \int\limits_{\vec{\ell}_{1}}^{\vec{\ell}_{2}} \vec{ F} \cdot d\vec{\ell}$$
it is ...
- 165
2
votes
2
answers
5k
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Can we define tension in a string as the reactive force produced in a string being pulled at both ends?
In my textbook, the definition of tension was given that Tension is the reactive force which exists when string is being stretched at its both end. After it there was a case given that to calculate ...
user66452
1
vote
1
answer
10k
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Derivation of formula of potential energy by a conservative force [duplicate]
the formula for potential energy by a conservative force is given by:
$$ F = -\nabla U(r), $$
which in one dimension may be simplified to:
$$ F = -\frac{dU}{dx} .$$
My question is how is it ...
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