All Questions
41
questions
0
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1
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80
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Where am I wrong in proving that force perpendicular to motion increases speed and kinetic energy? [closed]
Lets think of a helicopter flying at some height $h$. It throws a food packet to a person on the ground from air. Let's neglect the air drag.
The food packet is thrown only with some velocity $v_x$ in ...
- 85
1
vote
1
answer
29
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Describe the decrease in potential energy if two forces are acting on it one conservative which is greater than other applied by us in opposite dirn [closed]
So imagine this situation.
An object is experiencing two forces, one due to gravity in downward direction and other applied by us in upward direction such that our force is less than gravitational ...
- 13
0
votes
3
answers
113
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How does gravity do work to a horizontal projectile?
Suppose a ball is moving in a horizontal projection with some velocity $u_0$ in the positive $x$ direction. Here we see that although gravity is perpendicular to the velocity vector, it changes the ...
- 11
-1
votes
1
answer
283
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Increase in the internal energy of the block-surface system due to friction [closed]
I found this question:
https://plainmath.net/force-motion-and-energy/13968-block-dragged-horizontal-surface-acting-degree-horizontal-displaced
and I'm trying to understand why he used this formula to ...
0
votes
2
answers
55
views
Work done by gravity confusion
Say we had an object at height $h$ in a gravitational field, and of mass $m$, its GPE would equal $mgh$, now say we dropped it and it fell a distance of $h$, the work done on the object would be equal ...
- 195
0
votes
2
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86
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Is the topic of gravitational potential energy convoluted and unnecesary? [closed]
If we throw an object upwards from the surface of the Earth, we do some work on it to give it kinetic energy. Now as it travels up, Gravity of the Earth does negative work on it till it loses all the ...
0
votes
1
answer
54
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Why Gravitational Potential is same In Both these cases?
We usually choose Reference point as Infinity which is Linear to the Points
and by this way we gat work done as both force and displacement are in the same direction as well as in the same line which ...
- 121
0
votes
1
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115
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Why does the calculus derivation for Universal Gravitational Potential Energy not follow calculus laws and become $W=GMm/r$ instead of $W=-GMm/r$? [closed]
So we know that Universal Gravitational Potential Energy is $U=-Gm1m2/r$ where $G$ is the Gravitational Constant and $r$ is the distance between centers of mass. However, the derivation has me ...
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2
votes
2
answers
672
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Change in gravitational potential energy when the work is zero
I may be misunderstanding the whole concept , but my doubt is this.
Let us say there is an isolated system comprising of a rock and the Earth. If I was to lift the rock up with a force equal to the ...
- 71
0
votes
0
answers
57
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Confusion about an explanation for gravitational's potential energy
So we know that $\Delta U = -W$, where $\Delta U$ is the difference of potential energy and $W$ the work done by the force to move the body from point A to point B.
When analyzing this for the ...
- 21
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3
answers
1k
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From where does object gains gravitational potential energy?
If an object is moving upwards with constant velocity in which upward force is supplying energy and gravity is extracting energy till height ($h$), so from where it gained potential energy?
Please ...
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7
votes
3
answers
1k
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How is gravitational potential energy $mgh$?
I know the derivation that $W=Fd$, hence $F=mg$ and $d=h$ so energy gained by the body is $mgh$ considering the body on the ground to have $0$ gravitational potential energy.
But the definition of ...
- 1,168
0
votes
2
answers
272
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Limitations Of Work-Energy Theorem
Consider the given system which shows a chain $AB$ of length $l$ and the end $A$ is held at rest.
Suppose we release the chain at time $t=0$. How do we find the velocity of the chain when the end $A$ ...
- 117
0
votes
4
answers
510
views
How work done by a force on a body is negative?
The work done is the product of force acting on a body and the displacement of the body in the direction of the force.
The gravitational potential $\text{energy}=Mgh$ is the negative of the work done ...
0
votes
2
answers
420
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How much more net energy do I use walking up hill?
I have a question regarding work done / energy done.
Say a $70\mathrm{kg}$ man walked $100\mathrm{m}$ on a horizontal surface as a constant speed, is it correct to assume the energy done by this man ...
