All Questions
10,535 questions
1
vote
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158
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How long does it take a object captured by a star falling to the center?
If the captured object do not have tangential velocity, it's just the free-fall time. But when it has, it may take longer time to fall in, right ?
The function should be
$\ddot{r} = -GM/r^2 + (...
- 1,302
48
votes
8
answers
15k
views
Classical mechanics without coordinates book
I am a graduate student in mathematics who would like to learn some classical mechanics. However, there is one caveat: I am not interested in the standard coordinate approach. I can't help but think ...
1
vote
1
answer
2k
views
Relation of angular speed of a rigid body to Euler's Angles
My Question was like this and i have realised few things and still have some doubts
I have a book in which a paragraph goes like this
Now, $\dot\phi$, $\dot \theta$,
$\dot\psi$ are respectively ...
- 1,581
9
votes
5
answers
7k
views
How far does a trampoline vertically deform based on the mass of the object?
If a baseball is dropped on a trampoline, the point under the object will move a certain distance downward before starting to travel upward again. If a bowling ball is dropped, it will deform further ...
- 284
11
votes
6
answers
10k
views
What sustains the rotation of earth's core (faster than surface)?
I recently read that the earth's core rotates faster than the surface.
Well, firstly, it's easier to digest the concept of planetary bodies, stars, galaxies in rotation and/or orbital motion.
But, ...
- 1,187
14
votes
4
answers
77k
views
Which is easier, pushing or pulling?
It is generally assumed, from a person's perspective, that pushing a cart is more easier than pulling one. But why?
Is there any difference in terms of force required to achieve the same amount of ...
- 1,187
0
votes
2
answers
2k
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Transmission of energy in medium and wave nature (periodicity)? [closed]
Is there any example of a transmission of energy in a medium that does not show wave nature?
- 1,581
11
votes
2
answers
2k
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A problem inspired by the ice hockey game
Question shortly:
How far would a hockey puck slide in two different cases:
The puck is sliding (translation) on ice and spinning on its flat surface.
The puck is sliding on ice without spinning.
...
- 2,717
3
votes
3
answers
2k
views
Why is it hopeless to view differential geometry as the limit of a discrete geometry?
This is a follow-up question to Introductions to discrete space-time:
Why is this line of thought hopeless?
Classical mechanics can be understood
as the limit of relativistic mechanics
$RM_c$ ...
11
votes
3
answers
2k
views
Which direction will Coriolis forces deflect a bubble?
If I throw a ball straight up, it deflects slightly to the west due to Coriolis forces. If instead I watch a bubble float up in water, is the bubble deflected west, east, or neither?
I think the ...
- 53.7k
-3
votes
2
answers
315
views
Gravity and Collision of two continuous mass distributions [closed]
How could one explain the collision of two continuous mass distributions in view of
gravitation (Newtonanian and General relativity) ?
- 2,172
4
votes
1
answer
1k
views
Distinguishing mechanical systems from general dynamical systems
In the following let a "mechanical system" be a system of $n$ spatial objects moving in physical space.
Consider you are given a function $q:\mathbb{R} \rightarrow \mathcal{M}^n$ with $\mathcal{M}$ a ...
-3
votes
1
answer
528
views
What makes a space a real space? [closed]
By "real space" I mean a space in which physical particles move.
Consider a color sphere and let a bunch of objects "move" on its surface. "Move" means "change colors". Let there be some rules ...
23
votes
8
answers
5k
views
How to sail downwind faster than the wind?
Recently a group set a record for sailing a wind-powered land vehicle directly down wind, and a speed faster than wind speed. Wikipedia has a page talking about it, but it doesn't explain exactly how ...
- 331
12
votes
3
answers
1k
views
Imagine a long bar floating in space. What force does it exert on itself in the middle due to gravity?
Problem
If you had a long bar floating in space, what would be the compressive force at the centre of the bar, due to the self-weight of both ends?
Diagram - what is the force at point X in the ...
- 770
154
votes
9
answers
19k
views
Calculus of variations -- how does it make sense to vary the position and the velocity independently?
In the calculus of variations, particularly Lagrangian mechanics, people often say we vary the position and the velocity independently. But velocity is the derivative of position, so how can you treat ...
- 2,235
118
votes
11
answers
16k
views
Is Angular Momentum truly fundamental?
This may seem like a slightly trite question, but it is one that has long intrigued me.
Since I formally learned classical (Newtonian) mechanics, it has often struck me that angular momentum (and ...
- 7,458
7
votes
3
answers
4k
views
Constraint force on a rod
I really hope someone will take a quick look at the following, I would just love to better understand it...
This exercise is from Arnold's "Mathematical Methods of Classical Mechanics", p. 97 in the ...
- 2,456
3
votes
2
answers
2k
views
Question about moment of inertia and velocity
First off, I swear this is not homework. I'm doing some practice problems because I got an exam coming up. I'm stuck on this one:
I figured I would use energy conservation for this problem. So since ...
- 1,158
28
votes
10
answers
5k
views
Will a ball slide down a lumpy hill over the same path it rolls down the hill?
Suppose I have a lumpy hill. In a first experiment, the hill is frictionless and I let a ball slide down, starting from rest. I watch the path it takes (the time-independent trail it follows).
...
- 53.7k
1
vote
3
answers
214
views
What condition is fulfilled by the path of a mass sliding down a lumpy hill?
Suppose I have a hill that goes up and down unevenly. It's frictionless, and I want to slide a point mass down the hill. I am interested in the path it takes. (By "path" I mean the trail it leaves ...
- 53.7k
12
votes
6
answers
3k
views
Are the physical laws scale-dependent?
If you read the article "More Is Different", by P.W. Anderson (Science, 4 August 1972), you will find a deep question: are the physical laws dependent of the size of the system under study?
As an ...
- 600
5
votes
3
answers
713
views
How do molecules vibrate after collision?
The difference between kinematics and dynamics that Grisha pointed to in his answer comes up in a similar but slightly more complicated case:
Consider (in 1D) two point-like particles connected by a ...
6
votes
3
answers
1k
views
List of Scattering Phenomena
While at lunch with my lab group we got into discussion of the different types of scattering phenomenon that we encounter in everyday life and physical experiments. We ended up listing about a dozen ...
1
vote
3
answers
426
views
Where do atoms go after collision?
[I edited the question according to Mark's and Grisha's answers.]
Consider two point-like particles of equal mass colliding centrally in 2D. The final directions of the momenta of the two particles ...
4
votes
2
answers
2k
views
Does the friction force change directions with a change in reference frame?
In a basic friction problem with Block $A$ sliding on top of Block $B$ , the direction of the friction force is usually explained as being simply the opposite of the direction of motion. So if Block $...
6
votes
6
answers
3k
views
Simple three-body-problem?
Consider the problem of three bodies two of which having mass M, one of them having mass m. Body m is in the middle between the other two, coupled to them by two equal linear springs in rest. Now fix ...
3
votes
5
answers
2k
views
Why do we automatically assume that the velocity vector $\vec{v}$ and location vector $\vec{r}$ are independent? [duplicate]
I'm not sure if it's relevant, but I'm talking about a situation where a particle is moving in an electro-magnetic field.
As I understand, if we see the term $\nabla \cdot \vec{v}$ or $\nabla \times \...
- 2,130
-2
votes
2
answers
9k
views
Period of Precession [closed]
I'm trying to find the period of precession for a gyroscope. Now I was able to find the angular precession rate, which was 1.132 rad/s, but I have no idea how to convert this to a 'period', and google ...
- 1,158
-1
votes
2
answers
448
views
Angular Momentum and Force [closed]
I'm stuck on number 5. The answers to the first 4 are correct, but I dont know how to set up number 5. Any idea that I would have would require me having some kind of time information, but thats not ...
- 1,158
2
votes
2
answers
10k
views
Angular Momentum and Average Torque
Refer to number 6. This is the one I'm stuck on. So angular momentum is conserved right, so initial angular momentum is equal to final angular momentum. Initial is 7.87 so final must be 7.87, right? ...
- 1,158
6
votes
2
answers
9k
views
What determines the (minimum) angle at which a domino falls over?
Dominoes, when placed upright, remain that way. Sometimes, even if you tip them a little bit, they will go back to their upright position.
However, if you tip them too far, they will fall over.
...
- 6,030
3
votes
2
answers
8k
views
Finding angular acceleration from torque
We have to analyze this video
Givens:
An applied net torque due to the wind on the windmill is equal to $1500 \mathrm{\ N \cdot m}$.
Each (of the 3) propeller props weighs approximately $45 \mathrm{\...
- 1,158
15
votes
9
answers
3k
views
What are good mechanics experiments for 10 year olds? [closed]
I'm trying to explain elementary mechanics - without the benefits of calculus or even algebra - and struggling. I'd like to find reasonable ways to demonstrate Newton's laws, minimally, and possibly ...
29
votes
9
answers
26k
views
Book about classical mechanics
I am looking for a book about "advanced" classical mechanics. By advanced I mean a book considering directly Lagrangian and Hamiltonian formulation, and also providing a firm basis in the geometrical ...