# Tagged Questions

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

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### Photoelectric effect - elastic collision [on hold]

In an elastic collision, since the electron leaves with the same amount of energy as it originally had, does that mean the photon receives no energy? Does this even result in a photon emission, if so, ...
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### Can a person in a car hitting the interior of the car move the car?

As I remember, on old day explanation, a person in a car hitting the interior of the car cannot move the car, because there is no action and reaction force between the car and ground. But I doubt the ...
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### Newton's 3rd law… hitting drywall (which I break) vs hitting a brick (which breaks me)?

According to the Third Newton's law of motion: For every action there is an equal and opposite reaction. So, I understand that if I hit a brick wall with $50\, \mathrm{lbs}$ of force, the ...
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### How does this dumbbell rotate?

I am reading the book Spacecraft Attitude Determination and Control by J.R. Wertz, and on page 488 it says: My question is: how does the axis of rotation, $\hat{\omega}$, rotate? How does ...
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### Question regarding elastic collisions and the conservation of momentum / energy [on hold]

I've been working on this question for a few hours and I cannot quite convince myself that my answer is correct. I've read the relevant section in my textbook, but I guess the lightbulb just isn't ...
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### Principal moment of inertia for a rotating body

My major is not in physics. I am reading the following paper: (my problem is simple and not related with any optimization) http://arxiv.org/abs/1410.2841 (p.5~p.6) Suppose The ...
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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?
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 ...