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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How is the Principle of Conservation of Momentum proven using the Momentum-Impulse Principle?

Consider two particles moving in the same direction on the same line, $A$ and $B$, with mass $m_A$ and $m_B$, respectively. They also have velocies $u_A$ and $u_B$. They collide. After the collision A ...
2
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2answers
492 views

Does trade affect Earth's rotation? [duplicate]

Every country is trading with other countries around the world, some more than others. I was wondering if there would be any change to the Earth's rotation because of the imbalance of trade between ...
-2
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2answers
363 views

Determine whether the ground state is an eigenfunction of [p] and of [p^2] [closed]

Consider a particle confined in an infinite square well potential of width L, $$V(x)=\left\{ \begin{array}{ll}\infty, &{\rm for}\ (x \le 0)\vee (x \ge L) \\0, &{\rm for} \ 0 < x < L ...
3
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1answer
148 views

When a moving body collides with a stationary body, far from its centre, how do you calculate the resulting spin

Imagine you had a long heavy rod in space with no significant gravity acting upon it. And a projectile is flying towards it, perpendicular to the orientation of the rod, with the impact some between ...
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2answers
1k views

Momentum of a particle? [closed]

I really need help to understand what is momentum of a particle (of a photon, proton, an electron...) I see so many definitions! My main questions are: •What exactly is momentum •What are the ...
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0answers
174 views

Calculating rotor torque out of mass center

Suppose I have an engine with propeller. I know there is aerodynamic force pushing the propeller opposite direction the engine is turning it. One component of this force is creating lift, but second ...
0
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1answer
1k views

Expectation value of momentum

I'm having a problem with an expectation value that doesn't seem to add up for me. What I know is, that $\psi(\vec{r})$ is a wavefunction for a particle in three dimensions. The Hamiltonian is given ...
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0answers
60 views

Two impulses on body

Say I have a physics simulation with a single body with three degrees of freedom (two axis and rotation). I have two impulses of equal magnitude in opposite directions. When applying these impulses in ...
5
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1answer
2k views

How to derive the velocity in the double ball drop problem?

The double ball drop problem is as follows: A ball of mass $m$ is placed on top of a ball of mass $M$ (where $m < M$), and the balls are dropped simultaneously from some height $h$. When the ...
3
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2answers
614 views

Origin of motion and relative speed of bodies in the universe

Charged particles can hit the earth at relativistic speeds. But it seems that all large bodies have fairly low relative speed. Of course, speed can increase considerably when a body orbits close to a ...
5
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3answers
509 views

How can particles travel in a straight line?

A particle can be set off in a certain direction by giving them momentum. Momentum is a vector, so the particle heads off in a specific direction. But the wave function of the particle allows it to ...
0
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1answer
224 views

Kinetic energy when $F(t)$ graph is given

The very basic problem here is that the point where this graph ends is ambiguous. I mean, what is the corresponding $y$-value for the point whose $x$-valu is $4.5s$? Then I think we should find the ...
25
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1answer
713 views

Best current bounds on nonconservation of momentum?

It's not straightforward to test conservation of momentum experimentally, and many experiments that seem like tests really aren't. For example, in a Newtonian system of identical particles that ...
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2answers
480 views

Momentum, Impulse and Newton's Second Law of Motion

Newton formulated his Second Law as such: $$\sum{\vec{F}} = \frac{\delta \vec{p}}{\delta t}$$ and of course, $\vec{p} = m \vec{v}$. Why is it that if the net force $\sum \vec{F}$ is constant (which ...
0
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0answers
46 views

Schrodinger equation in momentum space [duplicate]

I have a problem this is: When I solve the Schrodinger equation in momentum space, I had done as this: $\begin{array}{l} i\hbar \frac{{\partial \Psi }}{{\partial t}} = - \frac{\hbar ...
2
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3answers
457 views

Two dimensional elastic collisions with varying angle of incident

If in an elastic collision I know all initial values and that mass for each object remains constant throughout the collision (but different from one another) how can I determine their final velocity ...
8
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2answers
280 views

How multiple objects in contact are resolved in an inelastic collision, when edge normals don't “line up”

In a case I understand, let's say I have an object A moving at velocity V toward 3 objects in contact B, C, and D: The momentum of A is the mass of A times its velocity. To figure out how the ...
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2answers
820 views

Simple conservation of momentum and frame of reference problem

I'm making a very simple physics engine based on momentum, and I'm solving what response to use for a collision from each involved object's frame of reference. However, something about how I'm ...
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6answers
879 views

Is there a momentum for charge?

Since mass and charge behave similarly, so, just like center of mass, I define a point center of charge, that is defined by $$\vec r_{qm} = \frac {\sum{q_i \vec r_i}} {\sum{q_i}}$$ where $\vec r_i$ ...
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3answers
1k views

What does it mean if a body has kinetic energy?

What does it mean if a body has kinetic energy? Does it mean that the momentum vectors of each particle of that body has the same direction? What about angular momentum?
4
votes
1answer
594 views

Conservation of momentum in collision of two bodies

Suppose we have some ramp on wheels of mass $M$, standing on a frictionless surface. A cart of mass $m$ moves with a certain velocity $v$ towards the ramp. The cart moves up the ramp ...
3
votes
1answer
976 views

General relativity and the conservation of momentum

I'm trying to understand the conservation of momentum in general relativity. Due to the curvature of space-time by matters and energy, the path of a linear motion appears to be distorted. Therefore ...
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1answer
1k views

Hermitian Adjoint of differential operator

I came across this equation (identity) (Eq. 4 in this paper): $\int(-i d\psi/dx)^*\psi dx = \int \psi^*(-i d\psi/dx) dx + id(\psi^*\psi)/dx\mid_{-\infty}^{+\infty}$ I have trouble proving it. I ...
4
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1answer
279 views

Firing machine question

Suppose we have a firing machine on a frictionless surface at point $x=0$. It fires a bullet of mass $m$ every $T$ seconds. Each bullet has the same constant velocity $v_0$. There's a body of mass ...
4
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2answers
296 views

Two-body problem questions

I am self studying the two body problem and I'm stuck on the following: I have given $$\ddot{\vec{x}}_1= - G m_2 \frac{\vec{x}_1-\vec{x}_2}{|\vec{x}_1-\vec{x}_2|^3}$$ and $$\ddot{\vec{x}}_2= - G ...
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1answer
597 views

Quantum mechanical analogue of conjugate momentum

In classical mechanics, we define the concept of canonical momentum conjugate to a given generalised position coordinate. This quantity is the partial derivative of the Lagrangian of the system, with ...
2
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1answer
504 views

Single photon's effect on conservation of momentum?

When your looking at basic Compton theory you find that if you shoot a stream of photons at a particle (usually atoms or electrons), then you have the basic laws of conservation of momentum. The ...
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1answer
440 views

Fundamental properties of motion

The first paragraph of the Wikipedia article on the angular momentum operator states that In both classical and quantum mechanical systems, angular momentum (together with linear momentum and ...
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1answer
99 views

Determine KE of electron given momentum & mass [closed]

Some info: wavelength of electron: $2.78 \times 10^{-10}$ momentum of electron: $2.38 \times 10^{-24}$ Determine KE of electron. In a provided hint: $KE = \frac{p^2}{2m}$. So I have: $$KE = ...
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6answers
767 views

Why is momentum conserved (or rather what makes an object carry on moving infinitely)?

I know this is an incredibly simple question, but I am trying to find a very simple explanation to this other than the simple logic that energy is conserved when two items impact and bounce off each ...
0
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1answer
225 views

Newton's second law?

$F=ma$. A car strikes a wall at 60 mph. Its acceleration is zero at the time. The force of the car against the wall or vice versa is? To look at the car the force is not zero. Please explain.
4
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2answers
4k views

Why is momentum conserved when a ball hits a vertical wall?

Almost in every book on physics, there's an example of conservation of momentum when the ball that is moving horizontally in the air, hits some massive wall. They claim that the return speed of the ...
4
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2answers
389 views

Conservation of Linear Momentum at the point of collision

This is a pretty basic conceptual question about the conservation of linear momentum. Consider an isolated system of 2 fixed-mass particles of masses $m_1$ and $m_2$ moving toward each other with ...
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2answers
342 views

effect of vertical collision on kinetic friction and subsequent change in horizontal velocity

Suppose somehow a block of mass $m$ is moving on ground, and the coefficient of kinetic friction between the block and the block is $\mu_k$. If I drop a tennis ball(of same mass) on it from a ...
0
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2answers
103 views

Minimum $E$ of $p\bar{p}$-collision for $q\bar{q}$ pair with mass $m_q$

I am currently working out the energy required to create a particle anti-particle pair from a collision of a proton travelling along the x-direction with an anti-proton which is at rest. The particle ...
2
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2answers
544 views

Movement of man and ladder and their center of mass

Suppose there is a massless frictionless pulley. A rope over it carries a mass $M$ and on other side carries a ladder of mass $(M-m)$ and a man on that ladder, of mass $m$. Now the man starts ...
3
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3answers
391 views

Where do the conservation laws come from?

I know the conservation of energy comes from Noether's theorem via the time-translational symmetry, and if I remember correctly, the conservation of momentum comes from space-translational symmetry. ...
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0answers
74 views

Need help with relativistic dynamics

I understand the concept, but I'm having a hard time applying the consequences of conservation (energy/momentum). For example: A proton with kinetic energy 437 MeV hits a proton at rest elastically ...
2
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3answers
493 views

How does the solar sailing concept work?

Wikipedia describes solar sailing as a form of spacecraft propulsion using a combination of light and high speed ejected gasses from a star to push large ultra-thin mirrors to high speeds. I ...
2
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1answer
341 views

Relativistic kinematics of particle decay

Suppose a particle decays to three other particles. The masses of all particles are assumed to be known and we work in the rest frame of the parent particle. So there are 12 parameters for this ...
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1answer
456 views

Inelastic collision and impulse

Suppose I have some cart moving horizontally in a straight line and with a constant velocity, and there is no friction between the surface and the cart. Now, I throw a plasticine on the cart at some ...
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1answer
8k views

Conservation of Momentum from Recoil Speed [closed]

A gun has a recoil speed of 2 m/s when firing. If the gun has a mass of 2kg and the bullet has a mass of 10g (0.01 kg) what speed does the bullet come out at? The gun has zero total momentum before ...
0
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0answers
427 views

Nuclear reaction: creation of deuterium

A proton p collides with a neutron(at rest) n at relatively low-energies and creates a 'deuterium-core' d: $$p+n->d+\gamma$$ Find the wavelength for the photon as a function of the proton's ...
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0answers
37 views

How do I find the force from drop shock using material properties?

I am dropping a cylindrical cast iron bar with a know elastic modulus and poisson's ratio, $E_{1}$ and $v_{1}$, onto a flat beam of elastic modulus, $E_{2}$ and $v_{2}$ so there is tangential drop ...
2
votes
4answers
560 views

Bat hitting a ball

When a bat hits a ball, consider two cases: 1) The batsman goes for a defense, and stonewalls it, to reduce its speed. 2) the batsman goes for a shot, e.g. a home-run, etc. in which case will the ...
1
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1answer
226 views

Shooting a bullet at a system of blocks [closed]

So, I made this question up myself.... and I'm curious about the answer. It requires only secondary-school-level knowledge of physics: You have a surface (ground) with a certain coefficient of ...
2
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2answers
221 views

A thought on definition of momentum

Well, this is a simple, basic and I think even silly doubt. The first time I saw the definition of momentum as $p = mv$ I started to think why this is a good definition. So I've read the beginning of ...
5
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4answers
427 views

Can a balloon be used as an anchor point for a pulley?

For a physics/ engineering contest, I want to use a large balloon as an anchor point for a pulley. This would allow me to raise and drop masses. However, in testing, when I pull on the pulley the ...
2
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2answers
1k views

Do photons actually generate a slight kinetic force?

My question is even though photons have no (rest) mass, do they emit a external force due to EM radiation causing electrons to be excited and jump to higher energy shells which electrons have mass ...
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2answers
15k views

Calculating force of impact

Since $\text{force = mass}\times\text{acceleration}$, is it right to say that an object traveling at a high constant velocity (zero acceleration), exerts zero force upon impact with a stationary ...