Tagged Questions
4
votes
0answers
45 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 ...
5
votes
2answers
163 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 $\vec r_i$ ...
3
votes
1answer
70 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 ...
2
votes
1answer
139 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 ...
0
votes
2answers
144 views
Perpendicular Elastic Collision (different masses, different velocities)
I'm stuck on a mechanics problem and I can't make any headway past momentum and kinetic energy being conserved. Here is the problem:
Two hover cars are approaching an intersection from ...
3
votes
2answers
157 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 ...
3
votes
2answers
58 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 ...
0
votes
5answers
173 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 ...
3
votes
3answers
190 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.
...
2
votes
1answer
116 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 ...
0
votes
2answers
64 views
Conservation of Momentum from Recoil Speed
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 ...
1
vote
1answer
70 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 ...
0
votes
2answers
402 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 ...
0
votes
1answer
159 views
Calculating a 2D collision between two perfectly circular disks
Assume I have two disks, $p_1$ and $p_2$, of radius $r$, with their own velocities (preferably in $(x,y)$ form, but $(m, \theta)$ works too) and masses (unit-less, but same unit) collide in two ...
0
votes
1answer
78 views
Combining Conservation Laws ~ Homework Problem Guidance
Problem 8.79 - Combining Conservation Laws
A 5.00-kg chunk of ice is sliding at 12.0 m/s on the floor of an ice-covered valley when it collides with and sticks to another 5.00-kg chunk of ice that is ...
0
votes
1answer
140 views
What happens if object is thrown in empty space?
If I throw a object in empty space, I apply a force to throw that.
Then it gains some acceleration and it's speed increases.
So will it's speed keep on increasing, or it will get stable?
If yes, ...
1
vote
1answer
70 views
How to get the new direction of 2 disks colliding?
I'm developing a 2D game including collisions between many disks. I would like to know how I can get the angle corresponding to the new direction of each disk.
For every disk I have this information ...
4
votes
1answer
154 views
What is the result of a classical collision between THREE point particles at the same precise instant?
Classical Mechanics is said to be deterministic, a statement that nearly always is followed by that quote from Laplace, something like
If at one time, one knew the positions and velocities of all ...
2
votes
3answers
173 views
Simple elastic collision
If a particle with mass $m$ collides with a wall at right angles, and the collision is perfectly elastic. The particle hits the wall at $v\ ms^{-1}$. There is no friction or gravity.
So the particle ...
0
votes
1answer
272 views
Kinetic energy in the center of mass
In a collision of a particle
of mass $m_1$ moving with speed $v_1$ with a stationary particle
of mass $m_2$ not all the original kinetic energy can be converted
into heat or internal energy. what ...
-1
votes
3answers
168 views
Classical mechanics and the speed of a train-mosquito collision, when perfectly rigid bodies
This is all under the assumption that they are perfectly rigid bodies:
A train is moving at 300m/s.
A mosquito is moving directly towards it, head-on, at 4m/s.
When the mosquito and the train ...
1
vote
3answers
130 views
Displacement with zero velocity
I know that we can rotate a deformable object using internal forces only in space. Thus we can cause an angular displacement without the use of any external forces.
The following youtube video shows ...
0
votes
1answer
114 views
Analysis of the impulse of 2 colliding carts under the effect of magnetic repulsion
Hi there! I have a question about an experiment that was conducted. It is related to momentum.
2 carts were put on a track on opposite sides. They were then propelled towards one another at ...
0
votes
1answer
193 views
What is the linear momentum of an inelastic and elastic collision?
The arrows in the figure represent the linear momentum of two balls before they collide. If the collision is perfectly inelastic, find the linear momentum after the collision. If the collision is ...
1
vote
1answer
96 views
Conservation of momentum with MOND
Assuming as true the phenomenological MOND law for low accelerations ($< 10^{-10} m s^{-2} = a_0$), and considering a small mass $m$ attached to a larger mass $M$ by a faint spring (let's think of ...
0
votes
1answer
101 views
Non-relativistic Kepler orbits
Consider the Newtonian gravitational potential at a distance of Sun:
$$\varphi \left ( r \right )~=~-\frac{GM}{r}.$$
I write the classical Lagrangian in spherical coordinates for a planet with mass ...
-1
votes
1answer
727 views
Violation of Newton's 3rd law and momentum conservation
Why and when does newtons 3rd law violate in relativistic mechanics? Check this link http://www.animations.physics.unsw.edu.au/jw/Newton.htm.
1
vote
2answers
150 views
Conservation of Linear Momentum with respect to a given direction
Is linear momentum conserved in any direction? More specifically, if you project all momentum vectors in a system onto another vector, will momentum be conserved?
I know that momentum is conserved ...
1
vote
2answers
959 views
Inelastic collision and conservation of linear and angular momentum
Is it possible for two spheres (a & b) to have an inelastic collision with BOTH the total linear and angular momentum preserved? I'm doing some physics simulation of some spheres attracting each ...
3
votes
3answers
392 views
Newton's 3rd Law: How can I break things?
If I punch a wooden board hard enough and it breaks in two, has the board still exerted a force of equal magnitude on my fist?
When the board breaks in two due to my force, the halves have a ...
3
votes
3answers
248 views
Conservation of Energy in Different Frames of Reference
Say I have a bucket of fuel that can produce 150J of energy by combustion. No matter what frame of reference an observer or the bucket of fuel is in, since the configuration of molecules stay the ...
3
votes
1answer
477 views
Conservation of linear and angular momentum
Suppose I have two rigid bodies A and B and they are connected by a spring which is attached off-center (thus possibly causing torques). Due to the spring a force $f$ acts on A and a force $-f$ acts ...
0
votes
2answers
155 views
Having Trouble With The Principle Of Conservation Of Momentum For a Multiparticle System
I'am reading John Taylor's Classical Mechanics chapter 1 page 20 where he proves the principle of conservation of momentum which states "If the net external force $F^{ext}$ on an $N$-particle system ...
4
votes
1answer
251 views
Is momentum conservation for the classical Schrödinger equation due to non-relativistic or due to some more exotic invariance?
I had no problem appliying the Neothers theorem for translations to the non-relativistic Schrödinger equation
$\mathrm i\hbar\frac{\partial}{\partial t}\psi(\mathbf{r},t) \;=\; \left(- ...
3
votes
4answers
737 views
Is it possible to lift yourself off from the ground?
Say for instance a person who was strong enough to lift double his body weight. If he placed his hands under his bottom and tried to lift$^1$ himself$^2$ off the ground, could he?
--
$^1$In a ...
0
votes
2answers
180 views
Conservation of momentum equation, how do I factor out v0Final and v1Final?
I am trying to figure out an equation for conservation of momentum. So,
If combined momentum before and after the collision is the same, and momentum is velocity times mass, then for 2 objects (A,B), ...
2
votes
3answers
197 views
Should any theory of physics respect the principle of conservation of angular momentum or linear momentum?
Is it possible that a theory that can describe the universe at the planck scale can violate things that we now consider fundamental in nature?For example can it violate rotational and translational ...
4
votes
2answers
279 views
Would a sneeze by a cosmonaut in a spacesuit affect his movement?
Naive question; feel free to shoot me down
It is a truism that any motion in space would continue indefinitely unless it is opposed by an external force. If a cosmonaut were to sneeze within his/her ...
1
vote
1answer
164 views
How to determine n equidistant vectors from point P in three dimensions
As an assignment for uni I need to figure out an algorithm that explodes a particle of mass $m$, velocity $v$, into $n$ pieces.
For the first part of the assignment, the particle has mass $m$, ...
-1
votes
2answers
225 views
Newton's Third Law - Action and Reaction on space, what happen with the astronaut? [closed]
This is a question from my homework.
Imagine an astronaut doing a repair in his ship, "parked" somewhere in space where gravity result is zero. As he can not do the repair, gets nervous and throws ...
-2
votes
1answer
104 views
Could a people do all sort of gymnastics movement in vacuum space? [closed]
Could a people do all sort of gymnastics movement in vacuum space? I asked this because I am worry about that the astronaut leave the space shuttle during emergency could not go back to earth by ...
0
votes
3answers
369 views
Will a stone thrown in space move forever?
If I throw a stone on space, in a place where gravity is equal zero, will the stone move forward forever, because no air, so no friction?
-3
votes
1answer
135 views
Mathematical question on Collisions [closed]
A 2.5kg ball travelling with a speed of 7.5m/s makes an elastic
collision with another ball of ...
-2
votes
1answer
380 views
Question on Impulse-Momentum theory
A 5kg stone kicked by a student undergoes a velocity change from 6m/s
to 10m/s in 4 seconds;
---- What is the momentum change of the stone within the time interval?
---- What impulse ...
6
votes
3answers
415 views
How does $F = \frac{ \Delta (mv)}{ \Delta t}$ equal $( m \frac { \Delta v}{ \Delta t} ) + ( v \frac { \Delta m}{ \Delta t} )$?
That's how it's framed in my Physics school-book.
The question (or rather, the explanation) is that of the thrust of rockets and how the impulse is equal (with opposite signs) on the thrust-gases and ...
1
vote
1answer
148 views
Rocket drive and conservation of momentum
I am currently reading through some lecture notes of Physics 1 and in a chapter about the dynamics of the mass point, there is an example covering the rocket drive.
Let $v$ be the velocity of the ...
2
votes
3answers
251 views
Train crash: are these situations alike?
I was just wondering... I believe that if a car travelling 50 miles per hour crashes into a wall, the result should be the same as crashing to another car also travelling 50 miles per hour (but in the ...
9
votes
1answer
234 views
Neutrino Oscillations and Conservation of Momentum
I would like to better understand how neutrino oscillations are consistent with conservation of momentum because I'm encountering some conceptual difficulties when thinking about it. I do have a ...
2
votes
1answer
225 views
momentum conservation question involving a rocket and a spaceship [closed]
With the engines off a space ship is cruising at a velocity of 230m.s
It fires a rocket straight ahead at the enememy vessel. The mass of the rocket is 1300kg and the mas of the ship (not including ...
0
votes
1answer
141 views
M1 vs M2 on a frictionless surface
I was wondering, if I had a frictionless surface and I had an M1 that was 100kg and an M2 that was 1kg and I pushed each separately with an equal force F would they move at the same speed or am I ...
