Tagged Questions
1
vote
2answers
55 views
Will a spinning object come to rest?
Will a sphere spinning on its own axis come to rest given enough time, provided no other forces act upon it?
I know that if you have two spinning spheres in the depths of space and orbiting each ...
3
votes
1answer
71 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
2answers
167 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 ...
2
votes
0answers
92 views
Elastic collision of rotating bodies
How would you explain in detail elastic collision of two rotating bodies to someone with basic understanding of classical mechanics?
I'm writing simple physics engine, but now only simulating ...
1
vote
1answer
71 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 ...
4
votes
2answers
92 views
Thrust center in space
I have this dilemma: Suppose you have a space ship somewhere in deep space, where there is no drag force or substantial gravity. If the ship has a single engine situated in such a way that the center ...
0
votes
1answer
162 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
145 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, ...
4
votes
1answer
155 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 ...
5
votes
3answers
499 views
Relationship between height and velocity in conservation of mechnical energy
I'm a high school physics student, and we recently did a lab on the conservation of energy where we measured the speed of a marble at varying heights on a rollercoaster track. We were supposed to ...
-1
votes
3answers
169 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 ...
1
vote
2answers
79 views
Ice skater increase of energy
This may be a very basic question but I am not seeing how it works.
Consider the standard example of an ice skate rotating about his/her center of mass and pulling in his/her arms. The torque is zero ...
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 ...
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 ...
1
vote
2answers
154 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
964 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
393 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
250 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 ...
0
votes
1answer
180 views
Scattering problem: Finding the speed of the scatterer after collision
A particle of mass $M$ moving in a straight line with speed $v$ collides with a stationary particle of the same mass. In the center of mass coordinate system, the first particle is deflected by 90 ...
1
vote
1answer
420 views
Scattering problem: Converting the two-body lab frame problem into a one-body center-of-mass frame problem
I'm reading the section on scattering in Goldstein's Classical Mechanics, and I have a rather basic question about this.
It says that scattering in the laboratory is a two-body problem because of ...
2
votes
1answer
371 views
Conservation of angular momentum across different reference frames?
I saw the following problem from the USAPhO:
A uniform pool ball of radius $r$ begins at rest on a pool table. The ball is given a horizontal impulse $J$ of fixed magnitude at a distance $\beta r$ ...
1
vote
1answer
346 views
What causes a force field to be “nonconservative?”
A conservative force field is one in which all that matters is that a particle goes from point A to point B. The time (or otherwise) path involved makes no difference.
Most force fields in physics ...
2
votes
3answers
828 views
Proving angular momentum is conserved for a particle moving in a central force field $\vec F =\phi(r) \vec r$
A problem I am trying to work out is as follows:
A particle moves in a force field given by
$\vec F =\phi(r) \vec r$. Prove that the angular momentum of the particle about the origin is constant.
...
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
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
105 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
373 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?
-2
votes
1answer
383 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 ...
0
votes
1answer
87 views
Period of an Object in Periodic Motion
My attempt (if it matters):
The initial period is given by $T_X = \frac{2\pi X}{v}$ for some $v$.
The new period is given by $T_Y = \frac{2\pi Y}{v}$ for the same $v$.
$Y = \frac{X}{2}$, so ...
5
votes
1answer
192 views
Effect of the tail of the cat in the falling cat problem
To explain why a falling cat can turn by 180 degree without external torque and without violation of the conservation of angular momentum, one usually models the cat as two cylinders as in
...
3
votes
0answers
73 views
Videos of changing the orientation of an astronaut in space
Kane, Headrick and Yatteau describe in their paper "Experimental investigation of an astronaut maneuvering scheme" possible maneuvers to change the orientation in space without external torque. Is ...
3
votes
3answers
534 views
How do the Planets and Sun get their initial rotation?
How do the Planets and Sun get their initial rotation?
Why do Venus and Mercury rotate so slowly compared to other planets and why does Venus rotate in a different direction to Mercury, Earth and ...
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 ...
2
votes
1answer
227 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 ...
