All Questions
60
questions
122
votes
10
answers
17k
views
How can I stand on the ground? EM or/and Pauli?
There is this famous example about the order difference between gravitational force and EM force. All the gravitational force of Earth is just countered by the electromagnetic force between the ...
- 1,321
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
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
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
26
votes
14
answers
4k
views
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 ...
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 ...
15
votes
2
answers
20k
views
What is the cause of the normal force? [duplicate]
I've been wondering, what causes the normal force to exist?
In class the teacher never actually explains it, he just says "It has to be there because something has to counter gravity." While I ...
- 253
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
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
6
votes
1
answer
1k
views
Resemblance between Coriolis force and magnetic part of Lorentz force
If we interchange velocity with charge and omega that is rotation of a system with $B$, magnetic field, we get the same thing. Is there any deeper meaning to this same mathematical form?
- 1,803
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
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
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
4
votes
1
answer
172
views
3 current loops with non-conservation of momentum, when one specifically considers SIGNs
Thought experiment I.
Consider two loops of wire, 2 small dipoles B and C , with a common axis z (facing each other) and (say) 30 cm apart B to C. At the speed of light, information (including a ...
- 101
3
votes
2
answers
507
views
Does constraint for speed of Electric and magnetic fields violates Conservation of momentum or Newton's third law?
I'm just a beginner so bear with me. Consider two frames at rest wrt to each other separated by distance enough for light to take a minute or so. At a given instant we create two large dipoles by some ...
- 31