All Questions
87
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2
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113
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Paradox? Why does energy conservation appear to be violated in this simple geared system?
While answering a question about gears and levers, I found I could not get the work in to equal the work out in this simple gear system illustrated below:
The gears are set up to replicate a lever, ...
- 6,102
0
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2
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41
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Where did potential energy disappear in this case?
Just a new thought experiment. We know that the kinetic energy depends on frame of reference as do work and velocity. Now we can consider a falling ball. It converts potential energy to kinetic energy ...
- 11
0
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2
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76
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Question related to conservation of energy
Here is a textbook passage that I have trouble understanding. It is taken from Classical Mechanics by Tom WB Kibble and Frank H Berkshire.
We consider first a particle moving along a line, under a ...
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-1
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3
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426
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How does gravitational potential energy work in a very large distance?
Consider a thought experiment (that I made when I was in high school) involving a universe with only two objects: a massive planet and a small asteroid. Initially, they are millions of light-years ...
- 109
1
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4
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204
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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
1
answer
83
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Kinetic energy conservation in different reference frame
Let us assume that there is a bowl fixed on a table. The radius is R. There is a small ball on the top such that it has a potential energy of $mgR$. When the ball is dropped, at its lowest point it ...
- 71
3
votes
4
answers
755
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Why do we say that gravity did work on an object to give it velocity, when it already had that energy as a potential?
I'm having a crisis of intuition here.
Scenario
A person takes a dive from a cliff. The person has a potential energy of $E_p = mgh$. As the person falls, they build kinetic energy, and lose potential ...
- 163
0
votes
1
answer
46
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Why is energy not conserved in some cases? [closed]
I've got a lot of cases where the energy of the whole system is not conserved, that's probably because of some non conservative force.
One reason is that, the energy is transferred to heat, which is ...
- 21
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2
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561
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How is the net work done on an object equal to the change in kinetic energy?
Let's say we have a ball at a height $h$ at rest. The total energy is $mgh$ which is the ball's potential energy. If we drop the ball, given that no external forces act on it, when the ball reaches ...
- 139
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votes
1
answer
101
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Why does a spring have potential energy compared to a rod?
From what I understand, a solid body or rod should not add work to a system.
This is because these bodies internal forces are passed through touch:
If the action and reaction forces are applied at the ...
- 1
0
votes
3
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594
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Why we say that total energy should be zero at infinity in the derivation of escape velocity?
I am little confuse about escape velocity. I have been taught that potential energy is arbitrary and hence we always assume it zero at infinity but actually it can or cannot be zero. My question is ...
- 121
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2
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106
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Distribution of Potential and Kinetic energies of a system consisting of two charges
Say we have two opposite charges with charge $+q_1$ and $-q_2$, and we'll refer to them by $+q_1$ and $-q_2$. Originally, they are separated at a distance of $d$. Now while keeping only $-q_2$ at rest,...
- 109
0
votes
1
answer
380
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Gravitational Potential Energy Lab Confusion
I had a lab that tested the dependence of gravitational potential energy on its position and the goal out of each exercise was to see if kinetic energy equaled potential energy. A cart was on a flat ...
1
vote
3
answers
93
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Preventing the release of potential energy
Suppose I pull on the string of a bow without releasing it. My muscles are converting chemical energy (from food) to let the bow string stay at this position but this energy is not stored in the bow, ...
- 13
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votes
2
answers
110
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Is the amount of work done in this case equivalent to both potential and kinetic energy?
This diagram is from a New York State Regent's exam, and it got me thinking about some "obvious" things in energy conservation.
We have someone pulling a rope with 600 N of force at an angle....
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