All Questions
60
questions
0
votes
1
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59
views
Force on a Charge
I apologize, as this question is quite basic.
Suppose we have a point mass of mass $m$. Suppose it is at position $r(t)$ at time $t$. Then the magnitude of the force on this mass is $\ddot r(t) m$ ...
0
votes
1
answer
83
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In classical electrodynamics, what are the equations of motion for a pair of point charges?
I know the equations for a (point) charge in a background electromagnetic field, and for the electromagnetic field due to a fixed current. What are the general equations, for the evolution of an ...
- 133
78
votes
4
answers
11k
views
How exactly is a normal force exerted, at the molecular level?
I've been surfing the web for quite a while, finding the answers I would need, but couldn't find a convincing one. First of all I need to remind you that this a very long/continuous question, so ...
user226894
1
vote
2
answers
60
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What are the ways of applying force axially, without any contact, to a rotating object? [closed]
Is there any other method except just using permanent magnets ? What are the advantages and disadvantages of using the various methods ?
0
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2
answers
269
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Would a horizontally-imbalanced maglev train car be propelled by the force of gravity?
I am wondering if a horizontally-unbalanced maglev train car would be propelled forward by the pull of gravity. This would result from the train car's electromagnets producing unbalanced magnetic ...
user217618
9
votes
3
answers
2k
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Where does a normal force come from?
Being more specific, let's say i place an object on top of a table, this will result on the table applying a normal force on the object.
My question is: Why does this force exists? Is it because of ...
- 93
2
votes
3
answers
827
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Using newton's third law in electromagnetism and special relativity problems
I am confused with using newton's third law in electromagnetism problems which includes Lorentz transformation.
In what conditions does this law holds?
for example, if there is an infinite charged ...
- 23
1
vote
2
answers
299
views
How does the system of particles respond to the external force?
If I push a box forward, then probably, the force I apply can be considered external force acting on the system of particles of the box. In rigid bodies like the box, each particle of the body should ...
- 885
1
vote
3
answers
433
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Does a force perpendicular to the direction of movement not do work?
I have read that since the magnetic force acting on moving charge is always perpendicular to the velocity of moving charge, the field is not doing any work on the charge.
However, if a ball rolling ...
- 261
0
votes
2
answers
299
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Magnetic Lorentz law and Newton's third law
If a charged particle moves in magnetic field it experiences Lorentz force given as :
$$\vec F = q \vec v \times \vec B$$
But I couldn't find a place where a reaction force as per Newton's third law ...
user170363
2
votes
3
answers
426
views
A broader view on contact forces
I am aware that all the contact forces we experience like tension, friction, normal reaction, et cetera are complex manifestations of the fundamental forces which are gravitational forces, ...
- 1,147
1
vote
1
answer
516
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What is the difference between the contact force and Tension?
Both are electromagnetic forces, yet why does tension pull whereas the contact force pushes?
It is not like a rope has some material which can pull, if a slack rope is just kept on a table then it ...
- 451
1
vote
2
answers
4k
views
Forces acting on a magnet and paper clip
Suppose a paper clip is stuck to a surface, with tape for example. A magnet is placed close to the clip, and starts moving towards it. Now, there is a force acting on the clip from the magnet, but is ...
- 113
25
votes
6
answers
4k
views
What kind of force can a rock exert which a motor cannot?
Imagine a dam with two doors. We have two cases:
First case: there is a rock heavy enough to stop the doors from opening.
Second case: there are are two motors or kind of machines (not sure if it ...
57
votes
4
answers
5k
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Is there an underlying physical reason why the Coriolis force is similar to the magnetic component of the Lorentz force?
I couldn't help but notice that the expression for the magnetic component of the Lorentz force,
$$\mathbf F = q\,\mathbf v \times \mathbf B\,,$$
is very similar in its mathematical form to the ...
- 2,463