# Tagged Questions

In introductory mechanics, the momentum of a particle is its mass times its velocity. In electrodynamics, the momentum of a field is proportional to the cross-product of the electric field with the magnetic field. In special relativity, momentum is generalized to four-momentum.

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### Physical meaning of crystal momentum

I am familiar with some of the definitions of crystal momentum and I am familiar with how it is related to Bloch's theorem. I also am familiar that crystal momentum is not the momentum of each ...
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### Impulse and momentum on a system of three particles (equilateral triangle)

I found this exercise on a textbook which provided solely the description of what is happening and the answers with little explanation. The solution being provided, I am mostly interested in ...
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### How can you calculate the thrust-to-weight ratio of a gun?

Is there some formula I can apply to the weight of a gun, along with the force of thrust it creates, and calculate if it will be able to lift itself off the ground or not? Without actually handling ...
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### difference between magnetic dipole moment and torque on a magnetic dipole?

I am a bit confused. What is the difference between magnetic dipole moment and torque on a magnetic dipole ?
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### Conversion of angular momentum to linear momentum in free space

If two objects both with angular and linear velocity collide in free space, can the total linear velocity of the objects increase at the expense of a loss in angular momentum? In other words, imagine ...
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### Why is this specific definition of acceleration used in deriving a general equation for kinetic energy?

$$\sum_{i=0}^n m_i v_i$$ as well as $$\frac{1}{2}\sum_{i=1}^n m_i v^2_i$$ Have been proved to be conserved by Newton & Leibniz, respectively. (http://en.wikipedia.org/wiki/Vis_viva) I don't ...
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### What is meant by conservation of momentum? [closed]

I need proof of this. Some examples are also required.
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### Inelastic collisions

During inelastic collision the kinetic energy does not remain constant. In many texts, I have seen it is because there is loss in energy from the system. If there is loss in energy, then how can mass ...
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### Rocket equation derivation mistake by my professor

In one of my lectures our physics professor gave a derivation of the ideal rocket equation as follows: Let $v_G > 0$ be the velocity at which the gas is emitted from the rocket. Let $m$ and $v$ be ...
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### Why is a network pattern (weaving pattern) stronger than a whole solid surface of the same material

For example badminton racquets and huts.
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### Is the Impulse-Momentum Theorem True? [closed]

This is just a general question I want to throw out there, and see arguments from both sides... Is Impulse-Momentum Theorem True? Well in my opinion I would say yes because it is a derived equation: ...
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### Change in momentum in a photon collision?

Let's say I drop a ball on the ground and it bounces up. According to classical physics, once the ball hits the ground it goes trough a short phase of deceleration until the velocity reaches zero, ...
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### Particle In a box, momentum, and velocity

On a homework assignment, we are give the width of a well $a$, the mass of the particle $m$, and we want to find the average velocity of the particle at the $n=1$ state. Here is my attempt at the ...
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### Can wind be defined as momentum/mass of air molecules?

In the past I thought a breeze of wind was "made" from a large amount of air molecules going all the same direction in the same speed. But it's not like that, actually this voted answer, this site, ...
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### Do gravitational waves contain actual energy and momentum? [closed]

Gravitational waves are waves in the fabric of space time and gravity is also caused by warped space time. So do gravitational waves contain actual energy and momentum?
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### How can momentum but not energy be conserved in an inelastic collision?

In inelastic collisions, kinetic energy changes, so the velocities of the objects also change. So how is momentum conserved in inelastic collisions?
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### Is momentum of a moving body a vector or a scalar quantity?

Is momentum of a moving body a vector or a scalar?
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### deformation and displacement by a collison? [duplicate]

In an experiment by Emilie du chatelet metal balls were dropped from a height on a clay bed only to find that the displacement of the clay material was proportional to the square of velocity of the ...
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### Relationship between impact crater properties and kinetic energy? [duplicate]

William Gravesande in 1722 published an experiment in which brass balls were dropped from varying heights onto a soft clay surface. He found that a ball with twice the speed of another would leave an ...
An object ofass $5$ kg is projected with a velocity of $20m/s$ at an angle of $60degress$ to the horizontal. At the highest point of its path projectile explodes and breaks up into $2$ fragments of ...