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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128 views

How do momentum get transferred?

Simple Question , Consider two objects namely $A$ and $B$ where $B$ is stationary and $A$ is moving towards $B$ with velocity $v$. When the two objects touch each other what does actually happen ...
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38 views

Gravitons, photons and conservation of momentum

How can gravitons be emitted from a mass to cause an attractive force to another mass? The same question could be asked of attractive e-m forces as well. Don't these violate the conservation of ...
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22 views

Can you do an n-body simulation in terms of energy and momentum?

An N-body simulation typically works directly in terms of the gravitational forces and accelerations. If you can solve the equations exactly, this is fine, but there are many instances where this is ...
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2answers
101 views

Optimal curve for a marble drop [closed]

I'm doing a marble roller coaster project for my physics class at school. The first part of our roller coaster involves a marble falling downwards into a curve that will drop then go up 12 inches. ...
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2answers
77 views

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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1answer
82 views

What is the reason behind the equation $p = mv$? [duplicate]

Now this is a very basic question, might look stupid too, but I am not able to understand it. I tried to imagine what momentum really is, and it is the impact of an object. I understood how momentum ...
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1answer
70 views

Annihilation process and photons [closed]

Why should two photons produced by the annihilation process move in opposite direction? I know you would say for the conservation of momentum but why can't they move in the same direction, I want to ...
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0answers
24 views

How does a bikerider turn by leaning on one side? [duplicate]

I am trying to understand the following image: Could someone please help me understnding it. What I understood so far: Your angular velocity mutyplied by the impulse gives you the impulsemoment. By ...
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1answer
60 views

Angular Momentum and Kepler's Second Law

Let me preface by saying that I get the gist of the conservation of angular momentum, at least qualitatively. To better illustrate my question, I will consider the case of a planet orbiting a star. ...
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61 views

How can we solve 2D rigid body collision? [duplicate]

I know that usually collision with velocity collinear can be solved by simultaneous equations of both conservation of energy and linear momentum. But my question is when 2D velocity is encountered, we ...
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1answer
175 views

Conservation of linear momentum and velocity of a system (damper and spring in a series)

This example is from a book on dynamics. Let us consider the system above formed by two blocks (each of mass $m$) connected by a linear damper and spring in a series. They slide without friction on ...
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2answers
110 views

Shifting momentum by a constant in the Schrodinger Equation

My book states that if we perturb a given Hamiltonian for the Schrödinger Equation $$ H = \frac{p^2}{2m} +V(x) $$ to $$ H' = \frac{p^2}{2m} + V(x) + \frac{\lambda p}{m} $$ then we can rewrite ...
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68 views

Is momentum conserved in this system?

We have a mass initially at rest on a ramp/wedge of arbitrary shape (i.e., not necessarily a triangle). There is no friction anywhere (including no friction between wedge and table). (1) Am I ...
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1answer
60 views

What is 'momentum outflow'?

Feynman, in his lecture, on Field momentum, used this term while relating the momentum of matter the field is interacting with & the field's momentum itself. Here is the excerpt: Just as the ...
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3answers
105 views

A moving bus suddenly stops. Is its momentum destroyed?

Absolutely not but how does momentum transfer to surrounding (ground, air particles)?
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6answers
129 views

How is momentum conserved when is is only dependent on mass and velocity, and so many other factors come into play?

I've been trying to get a good grip on the difference between conservation laws. Momentum is particularly tricky, I don't understand how quantities like $m\mathbf v$ can be conserved when other things ...
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2answers
98 views

Momentum conservation in the one-loop contribution of the photon propagator

The lowest contribution to the photon self-energy is represented by the following diagram (Taken from F.Schwabl, Advanced quantum mechanics, p.365):: ($k$ is the momentum of the photon that decays in ...
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111 views

Why Use the Non-Relativistic Momentum Operator in Relativistic Quantum Mechanics?

In deriving the Klein Gordon equation one starts out with the relativistic energy relation E^2 = p^2 + m^2 and substitutes the quantum momentum operator that corresponds to non-relativistic QM, p = -i ...
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1answer
72 views

Clarification in deriving the radial momentum operator $p_r$

In deriving an expression for $p_r$, a particle's radial momentum, I am unsure what is happening at a certain step. The derivation given in The Physics of Quantum Mechanics by Binney and Skinner is as ...
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1answer
50 views

How do I solve for $v_2$ where $mv_1^2 + MU_1^2 = mv_2^2 + M U_2^2$ and $MU_1 - Mv_1 = MU_2 - mv_2$ by eliminating $U_2$?

I was trying to solve the head on collision slingshot problem where the rocket moving with speed $v_1$ approaches a planet which is moving with speed $U_1$. I wanted the final speed of the rocket ...
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0answers
31 views

Probability of measuring an observable $P$ in state $f$, computation [duplicate]

I have state vector $$f(x)=e^{-|x|+ix}$$ and observable $$P=-i\frac {d} {dx} $$ probability that measurement of $P$ in state $f$ will be in $[-1,1]$ I am stuck on this step. I dont know how to take ...
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2answers
196 views

Derivation of canonical position-momentum commutator relation

We know that the position-momentum commutator is fundamental in quantum mechanics, but would it be possible to derive it starting from a different set of first principles, more specifically starting ...
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1answer
149 views

Application of Heisenberg's uncertainty principle on photons

While I was hobby-reading about quantum mechanics I came across Heisenberg's theory. But while I was trying to understand it I thought of this: if the speed of light (as well as the momentum of a ...
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1answer
135 views

Rolling Friction Problem

The handbrake of a vehicle of mass $1.5\ \mathrm{tonnes}$ completely fails while it is parked on a $30^\circ$ slope. It rolls $20\ \mathrm{m}$ down the slope before colliding with, and locking on to, ...
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1answer
95 views

How does a pop pop boat work?

I have been reading about the pop pop boat on wikipedea. What I don't understand is after the hot water is ejected the vacuume gets created, so when the same amount of water will be sucked in the boat ...
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50 views

Elastic Collision of Infinitely Large Body and an Infinitely Small Body

So I guess this is a somewhat conceptual question. There are two bodies, one with a mass $m$ that is so light it is massless and at rest so $v_{_i1} = 0$ And the other with mass $M$ that is almost ...
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88 views

Operator algebra for momentum and magnetic vector potential

Let $\vec{A}$ be the magnetic vector potential and $\vec{p}$ be momentum. $$ \vec{p} \cdot \vec{A} \psi = (\vec{p} \cdot \vec{A}) \psi + \vec{A} \cdot (\vec{p} \psi) $$ $$ \vec{A} \cdot \vec{p} \psi ...
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1answer
47 views

How impulse relates to momentum? is this correct?

Knowing that: $$F=\frac{dp}{dt}$$ I manipulate the equation a bit to say: $$Fdt=dp$$ Then ingrate both sides... $$\int{F}dt = p$$ From what I've read, isn't the change in momentum related to the ...
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2answers
122 views

What happens when two bodies collide in a dynamics point of view?

I'm a high school student learning about energy and momentum. What confuses me is the things with elastic and inelastic collisions. I completely (in my opinion) understand those concepts in energy ...
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1answer
30 views

How do i find how long an object can coast for?

I am given the mass of an object (a motorcycle), its velocity, the mass of its wheels, and the radius of the wheels. If the object rolls without slipping, how can I possibly find out how high it can ...
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2answers
60 views

Momentum Equation VS Momentum of Momentum Equation

Newton's second law states that the linear momentum ($P$) rate is equal to the net force: $$F=\frac{d}{dt}P \tag{1} $$ On the other side, there is a same expression for angular momentum ($L$): ...
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142 views

Conservation of mechanical energy isn't giving me the right answer? [closed]

I have been trying to solve this question: You are working for a shipping company. Your job is to stand at the bottom of an 8.0 m long ramp that is inclined at 37 degrees above the horizontal. You ...
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1answer
71 views

Do particles also have intrinsic linear momentum (linear analogue of spin)?

We know from quantum mechanics that microscopic particles have spin, which is a kind of intrinsic angular momentum. The particle has angular momentum without physically rotating. In a similar way, do ...
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1answer
48 views

Law of conservation of momentum , elastic collision [closed]

In Law of Conservation of momentum , elastic collision occurs only in an isolated system. A case defined as,when Object A comes with initial velocity and collides with object B which is in rest V= ...
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1answer
34 views

Rigid Balls aligned along a line in vacuum

Recently I've been trying to visualize a situation where i have these really rigid identical balls aligned along a line so close to each other in vacuum.Now if I were to apply an impulsive force to ...
2
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2answers
169 views

Is the reaction force for a stone hitting a wall infinite?

Let us assume a rigid stone which moves in empty space with a constant speed of $v$. (Or in the air with no friction and drag or you can imagine a free fall with friction). This stone hits a rigid ...
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17 views

Motion in Spaces [duplicate]

How does a shuttle move in the space as, the whole mechanism of a rocket is based on 3rd law of newton but, we can not apply 3rd law of newton in space because there is no reactive force in space?
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2answers
75 views

Conflicts between Bernoulli's Equation and Momentum Conservation?

The well known Bernoulli's equation states that $P+\frac{\rho V^2}{2}=c$ However, a simple momentum conservation considering $P_1$ and $P_2$ acting on two sides, and velocity changes from $V_1$ to ...
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3answers
153 views

Derivation of momentum operator

From a video lecture on quantum mechanics at MIT OCW I found that you didn't need to know Schrödinger's equation to know the momentum operator which is $\frac{\hbar}{i}\frac{\partial}{\partial x}$. ...
4
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2answers
108 views

How can photons cause charges to attract? [duplicate]

Photons are the force carrier of the electromagnetic force. I do not see how this could result in a transfer of momentum that attracts objects together. I am primarily interested in an intuitive ...
2
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1answer
91 views

When are energy, mechanical energy, momentum, and angular momentum conserved?

I am in AP Physics and my only real hangup is knowing when the said quantities are conserved. Please define what is the SYSTEM in your answer. I kind of have the basic idea. For example, if there ...
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0answers
23 views

How is conservation of momentum preserved in antimatter annihilation? [duplicate]

If an anti-proton collides with a proton, they are supposed to totally annihilate each other, correct? Then how is conservation of momentum preserved? Could you launch both protons and antiprotons ...
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0answers
40 views

Will the flash light accelerate in space? [duplicate]

As we know from school physics course light has pressure. So my question is will flash light accelerate in space in the direction opposite to light emission? If not, then will flash light with ...
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2answers
70 views

Which has the larger change in momentum [closed]

This is a concept question in my physics class, It isn't for marks, its just to gauge your understanding of the subject. I'm not sure if I have the right idea. since the mass of block A is 4 times ...
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0answers
41 views

Relativistic momentum (Lorentz boost) low velocity expansion

If I have a momenta $p^{\mu}=(E, p_x, p_y, p_z)$ and transform it via lorentz boost in x-direction with velocity v I'll get for the new 0th component $E'=\gamma E + \gamma v p_x$ why is this in the ...
2
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1answer
53 views

Simple frame of reference problem (conservation of momentum?)

I'm having trouble wrapping my head around a particular concept. Suppose we have a machine that fires balls of speed $u$ at some mass rate $\sigma$ (of units $\frac{kg}{s}$) directly at a car of mass ...
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65 views

Momentum operator derivation in QFT from QM

In David Tong`s QFT notes there is a chapter about the derivation of the momentum operator from quantum mechanics (page 44) where he is showing that the momentum operator can be expressed by the ...
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39 views

Conservation of momentum in inelastic conservation

Why does momentum and velocity change along contact normal but not contact tangent In in elastic collision? Suppose a ball strike an inelastic surface. It's velocity component does not change along ...
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1answer
8 views

Calculating the force $F$ for wich $S_2$ will be in uniform motion

The sketch is given: The double pulley groove of radius $r=5\;\mathrm{cm}$ and $R=10\;\mathrm{cm}$ is in rotation Two inextensible wires of negligible masses are wound around ...
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80 views

Does a conservation of momentum problem need to specify velocity, not just speed?

Problem: A $100$ g bullet is fired from a $10$ kg gun with a speed of $1000$ m/s. What is the speed of the recoil of the gun? This problem can be solved, if it can, using the law of conservation of ...