# Tagged Questions

The statement that a property of a system does not change if the system is isolated.

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### Movement of a box containig a particle [on hold]

A small thought experiment: Imagine a rectangular box in space, containing particle, all resting at $t=0$ from your point of view. At some point in time $t>0$ the particle starts to move with ...
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### How do rockets fly? [duplicate]

Is it that when a rocket loses its mass due to the escaping gases that results in its acceleration due to the same force acting upwards? If so, how is Newton's Third Law associated with it?
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### Hidden momentum

I'm trying to learn about hidden momentum. After reading what I could find with a google search, I understand that it is equal to the momentum carried by radiation, calculated with the Poynting vector....
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### Angular momentum in an accretion disk

I need to plot the time evolution of the total angular momentum in an accretion disc. This confuses me because I thought this should be constant, since angular momentum has to be conserved? I'm given ...
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### Collisions; Linear Momentum [closed]

Let's say we got a rough surface with friction and there are 2 blocks, the block of the left has initial velocity and will collide with the block of the right, which is in rest. Consider an elastic ...
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### Can a system's internal forces change the system's motion?

Let say the motor makes the two rigid body rotate as a same velocity. (they rotate the opposite direction) then the Net force of the motor is 2Fsin(Theta). The acceleration of the motor is 2Fsin(theta)...
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### Gravity and angular momentum

When a mass moves towards a bigger mass at a constant velocity, they will be attracted to each other such that the smaller mass will revolve around the bigger mass with the same speed as before. ...
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### Can internal forces bring any change in momentum of the system?

Imagine a rectangular box placed at the tip of an iceberg; the box contains a man who can freely walk/jump/rotate inside the box. The man walks up to one of the corners of the box and starts jumping. ...
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### What are some phenomena that can not be described without the help of Newton's third law of motion? [closed]

What are some phenomena that can not be described without the help of Newton's third law of motion? All the phenomena I can think of can be explained with the help of Newton's first law or second law. ...
The time translation is given by a finite unitary transformation $$\hat{U_{\tau}}(\hat{H}) = e^{\big(\frac{i}{\hbar}\tau \bar{H}\big)}.$$ Where \hat{U_{\tau}}(\hat{H})|\psi(t) \rangle = |\psi(t-\tau)...