All Questions
9
questions
2
votes
4
answers
187
views
Is the gravitational potential energy of an object on the ground 0? [duplicate]
In class, we were reviewing kinetic and potential energy and my teacher claimed that on the ground, objects have potential energy. However, as they cannot fall further, isn't their gravitational ...
- 539
6
votes
4
answers
2k
views
Why is gravity considered a negative vector in a pendulum question?
In many places and tutorials, gravity is often considered as a negative vector.
I am confused as to why is that? I though I was missing something from trigonometry but it was just negative in first ...
- 171
0
votes
2
answers
332
views
Reason for the negative sign in the gravitational potential $-GM/r$? [duplicate]
why the gravitational potential comes out to be negative that is $-GM/r$?
where G is gravitational constant
M is mass of the body
r is position at which the mass has to be brought from infinity.
- 21
0
votes
2
answers
708
views
Integrating a dot product gives wrong sign for work done [duplicate]
Consider a point mass which creates a gravitational field. The gravitational force pulls a 'test mass' towards the point mass. Since the displacement and gravitational force are in the same direction, ...
-1
votes
1
answer
492
views
Which is positive work and which is negative work when an object is lifted upwards by force A when already the gravity is acting on it from below?
If I lift a book upwards,then by which force is the negative work done; is it done by the force effected by me or by the force of gravity which is pulling the book from the ground below??
4
votes
6
answers
21k
views
Why is the work done in moving a unit mass from infinity to a point (where gravitational field exists) negative?
Gravitational force acts towards the center. Here, while performing work, force is towards the center and displacement is also towards the center, then why is the work performed on the body considered ...
- 439
0
votes
3
answers
8k
views
Derivation of gravitational potential energy
Change in potential energy is $$\Delta U = -\text{Work Done} \, .$$ While deriving the equation for potential energy we just equate the work done by gravitational force with the potential energy and ...
2
votes
2
answers
245
views
Confusion with $F=-\nabla V$, $F$ conservative
I am rather confused by the relationship $F=-\nabla V$.
If a pen drops from a height it loses potential energy so $\nabla V$ is negative. From the above equation this means that the gravitational ...
- 195
6
votes
2
answers
23k
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Work done against gravity [closed]
The work done against gravity is $mgh$, well at least that's what my textbook says.
I have a question:
I can apply a force say 50N, so total work done = $mgh + mah$. Where $ma$ = Force.
But the truth ...
