All Questions
22
questions
1
vote
3
answers
86
views
What is the actual meaning of $dx$ in $W=-F.dx $, in work in thermodynamics?
what I want to ask is that the $dx$ in that formula is the displacement of piston or the displacement of the center of mass of the gas. also is there any situation where this clarity is useful.
- 41
0
votes
0
answers
44
views
Energy Dissipated by Damper Infinitesimal Derivation
If we consider a damper (dashpot) element that exerts a force opposite the direction of motion proportional to the velocity, i.e. $$ \vec{F} = -c \vec{v}$$
Therefore, we can consider an infinitesimal ...
- 15
0
votes
3
answers
185
views
What does it mean in terms of energy if power is increasing with time? [closed]
Recently I have been studying work and energy and in this chapter I encountered with the term power. In terms of work power is written as $dW/dt$. So I have a doubt that suppose power is increasing. ...
- 37
0
votes
2
answers
52
views
Work-Energy Theorem for a path that is not smooth
In the analysis of Newtonian Mechanics for a single particle, we come across the definition of work and also the Work-Kinetic Energy theorem:
For a single particle, the work done on a particle by a ...
- 3,340
4
votes
4
answers
2k
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Help me understand the derivation of the kinetic energy formula please
In my physics textbook, kinetic energy is defined as $W$Net $=$ $\int m\frac {dv}{dt}$ $dx$ This makes sense to me just fine. The book goes on to rearrange the integral to say the following:
$W$Net $=...
0
votes
6
answers
116
views
Deriving Work-Kinetic Energy Theorem
I am currently reading Physics for Scientists and Engineers (Ninth Edition) by Serway and Jewett and in Chapter 7.5, a derivation of the work-kinetic energy theorem was shown.
To give context, ...
- 43
1
vote
1
answer
523
views
Acceleration as a function of displacement
I am given a question such that a 0.280kg object has a displacement (in meters) of $x=5t^3-8t^2-30t$. I need to find the average net power input from the interval of $t=2.0s$ to $t=4.0s$.
I know the ...
- 115
0
votes
0
answers
12
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Issue with work vs force for calculating spring constant [duplicate]
Lets say I have a spring with spring constant k. I put a 10kg weight on the spring and it compresses the spring one meter before stopping. We know that at this point the downwards force is equal to ...
0
votes
2
answers
178
views
How do we show that the work done by a variable force (in one dimension) is the area under the $F$ vs. $x$ curve?
In my physics textbook, to show that work is the area under the $F$ vs. $x$ curve, the author first writes the relation $dw = F dx$. This part makes sense to me. From there, the author writes, $$W = \...
- 1
0
votes
0
answers
126
views
Work-Energy Principle Derivation
I am currently in Mechanics I and both my professor and my book have derived the work principle in this way and I even asked about its derivation during class, but it has me puzzled.
I don't ...
2
votes
4
answers
633
views
Work done by a vector field (Force field) on a particle travelling along a curve
Assume a particle travelling along a curve, the work done by any Force field on the particle while moving along a curve is given by the line integral of $\vec{\bf{F}} \cdot \vec{\bf{dr}}$, but shouldn'...
- 367
0
votes
1
answer
120
views
Why can we multiply by $dt/dt$ to change variable of integration? Please look at equation 5-20 [closed]
I am struggling to understand why can we just multiply by $dt/dt$. I was thinking it was just a change of variables, but I cannot come up how that works. Can someone explain why we are allowed to do ...
- 37
1
vote
3
answers
65
views
Position Dependence in Equation of Motion
Our lecturer gives study material which contained that Newton's second law could be written as:
$$ \begin{aligned} F &= m \ddot{x} \\ &= m \frac{d \dot{x}}{dt} \\ &= m \frac{dx}{dx} \frac{...
- 13
5
votes
2
answers
301
views
Clarify definite integration of differentials in physics problems
I realized there is an issue with integration in physics problems that I had always taken for granted.
As an example, the relation between work and potential energy is
$dW=-dU_p$
when integrating ...
- 405
0
votes
3
answers
305
views
Issue with deriving the work-energy theorem
I'm a little confused regarding the way Total work = Change in kinetic energy is derived using calculus. My issue can be seen at 3:26 of this video: https://youtu.be/2dqO4sy4Njg?t=3m20s
Why can the ...
