# Tag Info

### Could someone give me the explanation for this scenario?

We are interested in the change in the ball's momentum during the collision. The collision takes place in a very short time interval: the average force required to affect a change in momentum so ...
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### Calculating momentum change?

let us look at what happens at the wall: the ball has incoming momentum in the positive x-direction, and departing momentum in the negative x-direction ; the momentum for the y-direction is the same ...
1 vote
Accepted

### Can we say the momentum of a system is always equal to the momentum of the components of the system?

Velocity of the system is better translated as velocity of the centre of mass. We can use the definition of centre of mass: $$\mathbf R{cm} = \frac{M\mathbf R_M + m\mathbf R_m}{M+m}$$ Taking the ...
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### Calculating momentum change?

Sounds to me, you are not familiar with vectors. So I highly suggest to learn about vectors quickly, which is a simple field of mathematics. Let's have a look in some more detail. x-axis points to the ...
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Accepted

### Force Problem with Punching Glove?

When you punch someone/something, you're applying an impact force on it and you yourself are experiencing the same force in return (of same megnitude but in opposite direction in accordance with ...
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### Calculating momentum change?

I'd recommend that you think first about a simpler case: you throw a ball straight at a wall (in the x-direction, let's say) and it bounces back with equal and opposite velocity. The wall has to exert ...
• 31.6k
Accepted

### Calculating momentum change?

One way to look at this is the following: for any system, you can relate the force the object experiences to its change in momentum by $$\Delta \vec{p} = \int \vec{F} \, dt$$ In particular, if the ...
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### Exact statement of conservation of momentum

Wikipedia's "in a closed system" and Taylor's "if there are no external forces on a pair of particles" are the same assumption, when applied to a pair of particles. In particular, ...
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### Why is maximal kinetic energy lost in a perfectly inelastic collision?

But just because the KE is 0 in some frame doesn't mean that it is the least possible in every other frame, does it? Yes, it does. Given two states with the same momentum, the question of which one ...
• 8,462
Accepted

### Adjoint of the Quantum Momentum Operator

Consider a vector space $V$ with an inner product $\langle\cdot,\cdot\rangle:V\times V\rightarrow\mathbb{R}.$ Given an operator $A:V\rightarrow V$, the adjoint is defined as the unique$^1$ operator ...
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Accepted

### Where is Conservation of Momentum derived from?

Conservation of momentum follows immediately from Newton's 2nd and 3rd law. For simplicity, I will assume a 2-particle system but the logic can be easily generalised to many particles. For the purpose ...
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1 vote

### Why do we drop the renormalization term in momentum Klein-Gordon Field Theory?

During quantization, classical quantities are typically replaced by normal ordered operators to ensure correct action on the vacuum state, cf. e.g. my Phys.SE answer here. Nevertheless, in OP's case ...
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Accepted

### Why do we drop the renormalization term in momentum Klein-Gordon Field Theory?

The normal ordering procedure in flat spacetime is nothing but the subtraction of the (infinite) contribution of the Minkowski vacuum. As a matter of fact, an added finite renormalization term could ...
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