All Questions
60
questions
0
votes
1
answer
47
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What happens when both magnetic field and electric field is applied to a charged particle?
Now what exactly happens when magnetic field and electric field is applied perpendicularly? What happens when they are not perpendicular?
In the question, it says that a magnetic field and electric ...
- 91
1
vote
0
answers
28
views
Which equation is most valid for finding power dissipation in a induced magnetic pendulum system?
Considering a set up where a conducting pendulum oscillates between two permanent magnets, I want to somehow calculate the power dissipated by the magnetic braking force the magnets provide, in order ...
-2
votes
1
answer
46
views
Propulsion of a spacecraft [closed]
If a craft is positioned at the strongest point of the earth's electromagnetic field being either positive or negative and the craft activates the same field it would repel each other would it create ...
0
votes
2
answers
69
views
Can the following set up be used to propel something upwards?
Let A and B be solenoids with the same pole facing each other.
Then will their repulsion cause the set up to jump upwards?
Please correct me if I am wrong:
Solenoid A exerts a downward force on ...
1
vote
0
answers
68
views
How do you calculate the force between an electromagnet and a piece of iron? [closed]
I am building a simple electromagnet, with an Iron core, and want to calculate the force it can exert on another piece of Iron when in direct contact with it (Basically how much weight it can lift). ...
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0
votes
2
answers
191
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Is tension a reaction force or an restoring force?what is tension then?what are the differences in them?
Assume a rope of mass $M$ is connected to a fixed wall and is free from other end
Now,I pull on the end of the rope
My simple questions are:
1.What is the reaction force/Newton's 3rd law pair force ...
- 161
0
votes
1
answer
54
views
If friction and normal force are both the components of contact force, shouldn't the friction be repulsive?
Is friction due to intermolecular attractive forces or repulsive ones.
Since both friction and normal force are the components of contact forces, shouldn't friction be repulsive.
3
votes
1
answer
204
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Why is normal contact force electromagnetic in nature?
I learnt that normal contact force can be interpreted as the restoring force when an object undergoes deformation due to external stress, and it is perpendicular to the surface of contact.
I also ...
- 85
1
vote
2
answers
102
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Does the force between two magnetic poles ever reach zero?
If we hold two magnetic like-poles together and start to move them away, would the repelling force reach absolute zero at certain point?
In that scenario, as a layman, I think that there is something ...
user342647
4
votes
2
answers
2k
views
Do Magnetic forces obey Newton's Third Law? [duplicate]
If we have two magnets and one is brought towards the other, the north of the former magnet is facing north of the latter. Now the other magnet is repelled which is obvious and Newton's third law is ...
- 817
1
vote
1
answer
139
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If contact forces are repulsive then how are we able to pull stuff? [closed]
I searched a lot on internet(especially physics stackexchange) about the nature of contact forces. I came to know through most of them that it is repulsive in nature which surely means that your hand ...
- 81
3
votes
2
answers
75
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Does it require greater force to accelerate a charged mass than an equal neutral mass?
Accelerating a charge produces radio-waves which is a form of energy. This energy has to come from somewhere. It would seem to suggest it would require greater force to move a charged mass than an ...
- 804
32
votes
6
answers
6k
views
If I push someone, what fundamental force do I create?
According to Wikipedia, all forces can be decomposed to four fundamental forces: gravity, electromagnetism, strong interaction and weak interaction.
When I push someone, this generates a force. Which ...
- 1,440
1
vote
1
answer
92
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Magnet A exerts an magnetic force $F_1$ on magnet B, B exerts a Reactive force $R_1$ on A, B exerts an magnetic force $F_2$ on A, is $R_1=F_2$?
Let's suppose there are 2 magnets, A and B, that are within the magnetic field of each other. Then A will exert a magnetic force on B (let's name it F1), and, due to the 3rd law of Newton, every ...
- 151
3
votes
3
answers
397
views
Detect reaction force to Lorentz force
If a charged particle is deflected in a magnetic field due to some magnet, is there any experiment that shows (or measures) the opposite reaction force (due to Newton's third law) on the magnet?
- 737
1
vote
1
answer
101
views
What feels the force that is equal and opposite to the Laplace force?
The Laplace force is the force applied to a current-carrying conductor in a uniform magnetic field:
$$ \vec F = I \vec l \times \vec B $$
It has been described as a macroscopic view of the Lorentz ...
- 111
0
votes
2
answers
87
views
How does magnet follow both law at same time newton 3rd law but also magnetic field?
have been wondering a question that:-
It is said that " magnet(say,Magnet no.1) has a magnetic field that informs in which direction the north pole (of other magnet or compass say , magnet no.2) ...
4
votes
2
answers
2k
views
Is Newton's law really invariant under Galilean transformation (for velocity-dependent Lorentz force)?
Consider the motion of a charged particle of charge $q$ and mass $m$ from two different inertial frames $S$ and $S'$ connected by Galilean transformation equation ${\vec r}'={\vec r}-{\vec V}t$. This ...
- 11.8k
1
vote
2
answers
100
views
How do we apply force on a body?
We know that force is apllied either by pushing or pulling anything.
But how do we push or pull or apply force on anything.
I imagine the object A that is pushing and another object B that is getting ...
user316791
0
votes
2
answers
170
views
Confusion regarding the origin of Normal reaction
While reading about the normal reaction for different scenarios, I faced minor confusion regarding their origin.
Suppose a mass is kept on a surface. The mass exerts a downward force indirectly due to ...
- 1,791
2
votes
1
answer
225
views
Magnetism rail problem
A circuit with resistance $R$ is given. The emf $E$ in the circuit is produced by a conducting rod moving with constant velocity in a uniform perpendicular magnetic field. The rod is sliding on ...
- 69
0
votes
0
answers
52
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Forces on a closed container that can electromagnetically suspend objects
If you have a closed container (without air or other fluids, only with the object inside) that can electromagnetically suspend or maintain (not like if the container walls are covered with a single ...
26
votes
14
answers
4k
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Explaining how we cannot account for changing acceleration questions without calculus
For context, I am a high school physics teacher.
I am teaching students about the basics of electromagnetic force between two point charges. The equation we use is $F=\frac{kq_1q_2}{r^2}$.
This gives ...
1
vote
0
answers
47
views
Unstable Equilibrium of hinged rods
I conjured up a scenario where there are two rods free to rotate about a hinge connected by their ends by spring of spring constant $k$,both their masses are $m$ and length $l$ and mass is uniformly ...
2
votes
2
answers
932
views
How is force transmitted across a body?
So I am leaning about various topics like physics like simple machines, center of mass, momentum, energy conservation, equilibrium but the more I study these "upper" level concepts the more ...
- 823
6
votes
4
answers
224
views
Action-reaction pairs with electromagnetic waves
Suppose that a tower is releasing radio waves. These waves are received by an antenna. The radio waves apply force to the electrons in the antenna. My question is that by newton's third law, every ...
- 71
0
votes
1
answer
314
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Newton's third law between moving charge and stationary charge
Between two stationary charges, Newton's third law holds. But what if one of the charge is moving? Like, in moving charge, electric field is different with the field generated by stationary charge.
...
- 266
4
votes
2
answers
742
views
Why friction is attractive force whereas normal reaction is repulsive?
Both friction and normal reactions are contact forces. And according to what my textbook states both are of electromagnetic in origin. If so why normal reaction, say a block on a table pushes it away ...
- 310
0
votes
2
answers
858
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Does an initial condition of "at rest" mean that the velocity is zero, but the acceleration could be nonzero?
I'm solving a differential equation for the relativistic motion of an electron in an electric field. The electron is initially at rest in the uniform field, but I am not sure if the initial condition ...
- 171
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2
answers
2k
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What are the different types of energy transfer?
[NOTE: The definition of work that I am using is the following-
Work is the transfer of energy that occurs to/from an object when a force acts on it to cause a displacement.
]
In my physics book ...
user238497
0
votes
1
answer
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
views
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
votes
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
views
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
views
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
views
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
views
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
views
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
views
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
1
vote
1
answer
6k
views
Can Newton's 3rd Law be considered as a direct consequence of the coulomb's law of electric interactions? [closed]
Let me explain my thought. Lets consider Coulomb's definition of electric force between two charges as the fundamental law. Under this consideration, forces between charges already follow What Newton'...
- 121
1
vote
2
answers
148
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Levitation using Electromagnets - Forces
Here is a hypothetical (but potential real) situation:
I am holding electromagnet that weights 1kg. This electromagnet is being used to hold up a 10kg weight.
Would I feel like I am holding 11kg, or ...
user100775
0
votes
1
answer
703
views
Will dynamo generate electricity with reverse spin?
Will a dynamo generate electricity when it is spinning in opposite direction? If we alternate the rotation direction every minute, will it still generate electricity? How?
- 121
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votes
1
answer
77
views
Should there be a linear force acting aside from torque?
Assume to identical motors are placed vertically on-top of a table and they are not fixed able to move/fall etc...and they have gears attached to them and are attached to one another like this image:
...
- 1,110
0
votes
3
answers
148
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Traveling to Mars in 24 Days
I am trying to calculate an electromagnetic rail launch from the Moon but I need to know if humans can survive the launch. Please see the specs below.
150 miles of track
Proposed final launch speed ...
- 13