All Questions
13
questions
-1
votes
2
answers
130
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Verifying $W = \int \vec{F} \cdot d\vec{x}$
Verifying formula for Work;
$$W = \int \vec{F} \cdot d\vec{x} \quad(i)$$
Let us consider a very simple scenario; I will solve first by simple Maths and then by calculus.
Scenario 1: (Force vector is ...
- 439
0
votes
3
answers
504
views
The Lagrangian for gravitational potential energy in a double pendulum
For a double pendulum what would be the gravitational energy. I am trying to work out the Lagrangian for the double pendulum. I got the kinetic energy but I am struggling on the gravitational ...
- 119
0
votes
3
answers
499
views
How do I get the negative sign in the expression for Gravitational Potential Energy?
From universal law of gravitation, gravitational force exerted on a body of mass m by another body of mass M is
$$ \mathbf F = \frac{GMm}{x^2} $$
where x is the distance between the ...
1
vote
3
answers
1k
views
I've a problem understanding Absolute Gravitational Potential Energy?
My current concept about potential energy is that 'If work is done on a body when it is at a point (taken as zero P.E), it covers some distance. Afterward, when it is allowed to move freely it does ...
- 164
1
vote
2
answers
306
views
Deriving gravitational potential energy - why is $r_0 = \infty$?
I'm wondering about some assumptions I have to make in deriving the gravitational potential energy. This arises from the following exercise:
-
Since the net force acting on the satellite is ...
- 3,200
1
vote
2
answers
673
views
Equations of motion for elastic pendulum [closed]
Having some trouble deriving the equation of motion in $y$-direction ($x(t)=0$).
It said in the problem description that the equation should be:
$$my'' = -\frac{dV(r)}{dy} -mg.$$
$y''$ is the second ...
- 19
2
votes
1
answer
135
views
Sign mistake calculating electrostatic potential energy formula! [duplicate]
I have a problem calculating the electrostatic potential energy.
I rely on these equations coming from mechanics:
\begin{equation}
U_{B}-U_{A} = -W_{A \ \rightarrow \ B} (done\ by \ the \ field \ ...
- 133
0
votes
1
answer
80
views
Conventions for work and energy are not going correct in this situation [closed]
Let us consider 2 objects A and B.
The initial PE of the objects be U(A)=10J and U(B)=0J. Let F be the force exerted by A on B. Suppose W be the work done by force F. Due to this the PE of both the ...
- 356
-1
votes
2
answers
639
views
Electric Potential produced by Hollow Sphere
Let there be a hollow sphere (Throughout the question we will ignore the thickness of the sphere) which is positively uniformly charged,q of radius, R. Suppose there to be a test positive charge, q' ...
- 356
1
vote
3
answers
569
views
Why isn't the work minus the potential energy when bringing a charge in from infinity?
This is an example in my physics textbook, and there is just one step that I don't understand.
Two point charges are located on the x-axis, $q_1 = -e$ at $x = 0$ and
$q_2 = +e$ at $x=a$. Find the ...
- 21
1
vote
1
answer
1k
views
Potential Energy in modified Atwood Machine
The initial length of the spring is $l_0$.
I need help understanding how the potential energy of this system comes to be. I know the answer:
$$
U = -(m_1-m_2)gx-(m_1+m_2)gy+\frac{1}{2}k(y-l_0)^2+...
- 197
2
votes
2
answers
184
views
My total potential energy?
The potential energy in a uniformed gravitational field is $mg \cdot \Delta h$. This assumes of course that $g$ doesn't change and only gives the difference in potential energy for $\Delta h$.
How ...
- 797
1
vote
2
answers
159
views
What is the zero of potential?
A satellite of mass $m$ is travelling at a speed $v_0$ in a circular orbit of radius $r_0$ around a fixed mass at $O$. Taking the zero of potential at $r=\infty$, show that the total energy of the ...
- 199