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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1answer
163 views
Momentum question?
The problem:
In a car crash, a passenger with a mass of 82kg is not wearing a
seatbelt. The car is travelling at 45km per hour. What impulse must
the car's airbag provide in order to stop the ...
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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 ...
-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 ...
-3
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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 ...
9
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1answer
233 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 ...
3
votes
1answer
1k views
How do kinetic energy and linear momentum relate?
It took me quite a long time to click my gears in place and even then I'm not sure it's completely correct.
The problem is that I need to understand these concepts (physics concepts; not just these ...
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 ...
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1answer
475 views
Finding force exerted in an Inelastic Collision
I did a lab today in Physics in which we launched ball from a spring loaded cannon directly into a pendulum that captured the ball, held it, and swung upwards with it (representing a totally inelastic ...
3
votes
1answer
393 views
Walter Lewin Lecture 16 - Ball bouncing on wall?
I never did Physics in university and I consider that a mistake so I am correcting that now by teaching myself. To that extent I have been watching the MIT lecture videos by Walter Lewin and I am ...
1
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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 ...
3
votes
2answers
154 views
Does constraint for speed of Electric and magnetic fields violates Conservation of momentum or Newton's third law?
I'm just a beginner so bear with me. Consider two frames at rest wrt to each other separated by distance enough for light to take a minute or so. At a given instant we create two large dipoles by some ...
4
votes
3answers
333 views
Conservation of Energy and Momentum Regarding Forces - clarification needed
The other day, my teacher stated something along the lines of, "Conservation of momentum is not violated by the actions of internal forces, but the conservation of energy is violated. Energy is ...
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1answer
110 views
How to explain relativistic mass with 2 moving systems, but not 3?
All the visual explanations I know work in some kind of "If you are moving relative to something A, while inside A something is moving, the stuff in A has to move slower due time dilation and ...
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3answers
1k views
A spinning bullet
I know the rifling in a gun or rifle puts a spin on the bullet along the axis of trajectory. Now I don’t understand exactly what does it make the trajectory more stable and the travel grater?
1
vote
2answers
341 views
When should we use the concept of Impulse/Momentum instead of Force?
In my notes it says
"The ideas of impulse and momentum is useful in solving problems where:-
a) the force F is not easily calculable (e.g. sudden impact or blow)
b) the impulse force is ...
-1
votes
1answer
253 views
Minimal kinetic energy during elastic collision [closed]
Two wagons, moving towards each other along a straight line, collide. The first wagon has the speed 3 m/s and the weight 3 kg. The second wagon has the speed 1 m/s and the weight 1 kg. The collision ...
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 ...
4
votes
4answers
501 views
Uncertainty Principle for a Totally Localized Particle
If a particle is totally localized at $x=0$, its wave function $\Psi(x,t)$ should be a Dirac delta function $\delta(x)$. Accordingly, its Fourier transform $\Phi(p,t)$ would be a constant for all $p$, ...
2
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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 ...
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votes
2answers
88 views
The time for which rear moving block remain in contact with spring in the following situation? [closed]
I'm a physics tutor. I'm stuck up with this question. I've no clue about how to proceed with this question. Can any one help?
A 2 Kg block moving with 10 m/s strikes a spring of constant π^2 N/m ...
2
votes
0answers
251 views
kinetic energy in collisions
We were hoping you could help us understand collision energy.
Vehicle A is driving West at 35mph and weighs 1437kg.
Vehicle B is driving North at 35 mph and weighs 1882kg.
Vehicle B crashes into the ...
1
vote
2answers
234 views
Connection between momentum and energy
What is the connection between momentum and energy?
Which of the answers is the correct?
A particle can have zero momentum but energy.
A particle can have zero energy but momentum.
...
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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 ...
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votes
2answers
483 views
Matter waves and de Broglie wave length
The wavelength of a particle of momentum p is calculated using De Broglie relation.
The de Broglie relation was postulated for what is called a matter waves. Now according to the statistical ...
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1answer
264 views
Force and Laws of Motion [closed]
While catching a fast moving cricket ball, why do fielders gradually pull back their hands backwards with the moving ball? Please advice which among the following is the correct answer. If both are ...
7
votes
7answers
2k views
Does leaning (banking) help cause turning on a bicycle?
I think it's clear enough that if you turn your bicycle's steering wheel left, while moving, and you don't lean left, the bike will fall over (to the right) as you turn. I figure this is because the ...
1
vote
2answers
239 views
Simple conservation of momentum
Imagine a particle moving right at 10 mph. It enters a cylinder with an open left end and closed right end. The cylinder is moving right at 1 mph. In the frame of reference of the cylinder, the ...
0
votes
2answers
251 views
Kinetic energy absorbing in order to avoid damages?
is this possible? To absorb kinetic energy and disable inertia force?
http://www.youtube.com/watch?v=KnKPbAbJI0w
http://www.youtube.com/watch?v=4_5oseSVUc4
3
votes
2answers
2k views
What is p_T? (transverse momentum?)
I've been looking at a few papers in experimental physics (from the ATLAS collaboration, for example) and I've often run across phrases such as "high-p_T electron." What exactly is p_T? Is it simply ...
3
votes
2answers
905 views
Conservation of Momentum/Energy collision Problem
I'm working on a physics problem in preparation for the MCAT and there's this particular problem that's troubling me. I don't know if it's a bad question or if I'm not understanding some sort of ...
1
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1answer
595 views
Converting angular velocity to linear velocity through friction
A very basic question here; it's related to this one, but not quite the same.
If a rotating rigid body (a sphere for the sake of discussion) with mass $m$, radius $r$ and inertial tensor $I$ has ...
1
vote
2answers
294 views
Conservation of momentum leading to damage
What would be an intuitive way to damage objects in a physics game using impulses? Since momentum is conserved, so is impulse (the change in momentum for any two time periods) in a closed system.
So ...
3
votes
2answers
128 views
“Dark” quantities
I don't know much about the so-called dark matter, apart from what has been described in popular descriptions of the reasons for it being postulated.
My question is, is there dark momentum, dark ...
4
votes
1answer
348 views
How do you combine two rigid bodies into one?
With respect to some fixed frame of reference, given the inertial tensors, positions, orientations, and angular and linear velocities of two rigid bodies, how do you combine them to make a single ...
1
vote
2answers
109 views
Is stopping something work?
If somebody pushes against a mass moving with $3 \frac{m}{s}$ to slow it down to $2 \frac{m}{s}$, he will drain the moving system of kinetic energy. Does he do work then or does he consume work?
My ...
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votes
0answers
81 views
Physics behind 2 different wall kicks
I'm looking at a situation where a sprinter starts at some distance x from a wall. The goal is to sprint to the wall, hit it, and get back to the start as quickly as possible. There are two ways ...
4
votes
4answers
225 views
Applications of recoil principle in classical physics
Are there any interesting, important or (for the non physicist) astonishing examples where the recoil principle (as special case of conservation of linear momentum) is applied beside rockets and guns?
...
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1answer
101 views
On a frictionless table, what is the angle at which a cue ball should hit another ball for it to go in?
Assume there are 2 balls on the table. Cue ball and another ball. What is the angle at which the cue ball should hit another ball for it to go in?
3
votes
3answers
1k views
Does conservation of momentum really imply Newton's third law?
I often heard that conservation of momentum is nothing else than Newton's third law.
Ok, If you have only two interacting particles in the universe, this seems to be quite obvious.
However if you ...
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1answer
64 views
Where can I find the equations for “quasi” elastic collisions?
Yes, you all talk about neutrinos and spins, but I came out with this basic s**t :D
All of us learnt the basic equations of collisions, elastic (everything bounces and energy remains the same), or ...
3
votes
5answers
221 views
Usefullness of an only qualitative understanding of momentum?
A few days ago I had a discussion with a friend who wants to become a physics teacher (in Germany). He told me that from a pedagogical/didactial point of view it seems to be a good idea to introduce ...
2
votes
1answer
716 views
Use the relative velocity formula to find v2f in terms of v1f?
Q:
A $0.150\text{ kg}$ glider is moving to the right ($+x$) on a frictionless, horizontal air track with a speed of $0.80\text{ m/s}$. It has an elastic collision with a $0.300\text{ kg}$ ...
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0answers
125 views
water / solid body momentum exchange [closed]
When water is sprayed a at a solid object weather flat or concave is the momentum exchange the same? Because when water hits the flat object it simply goes outward or perpendicular to the object but ...
4
votes
3answers
2k views
Hammer vs large mass on nail
Why is a hammer more effective in driving a nail than a large mass resting over the nail ?
I know this has to do with momentum, but cant figure it out.
6
votes
2answers
493 views
What are the properties of two bodies for their collision to be elastic?
For example, must the shock wave in each body be of a particular form which influences the shape and material properties of the bodies?
I suspect part of the the answer is that the objects must be ...
3
votes
2answers
855 views
Quantum momentum (De Broglie)
The de broglie hypothesis suggests a particle can be associated with a wave of
momentum $p = \hbar k$
my question is the following: how does one arrive at this concept of the momentum of a wave?
I ...
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1answer
182 views
Why electromagnetic waves propagating along x transfers to electron momentum along z?
Why EM waves having only x momentum transfers to electron z momentum? Electron begins oscillating along z, so will not radiate EM waves along z direction, to compensate its z momentum. It seems that ...
6
votes
4answers
958 views
Examples where momentum is not equal to $mv$?
I am aware that momentum is the thing which is conserved due to symmetries in space (rotational symmetry, translaitonal symmetry, etc). I am aware that in some systems, the generalized momentum,
...
3
votes
6answers
3k views
How does gravity affect bullets?
I read recently that if you hold a bullet in one hand and a pistol in the other, both hands at the same height, and subsequently fired the pistol at the same time as dropping the bullet, both bullets ...
3
votes
1answer
663 views
Confusion between the de Broglie wavelength of a particle and wave packets
So I learned that the de Broglie wavelength of a particle, lambda = h/p, where h is Planck's constant and p is the momentum of the particle. I also learned that a quantum mechanics description of a ...
