General questions about the way objects move and interact. This tag should be used when the tags for certain kinds of mechanics (newtonian-mechanics, classical-mechanics, quantum-mechanics, etc.) are too specific.
0
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0answers
17 views
Allowed Quantum States- Filkelstein and Rubinstein constraints
So basically i'm doing a report on Finkelstein and Rubinstein constraints. I have a system where the allowed quantum states satisfy ...
0
votes
1answer
107 views
Microphones, Loudspeaker and their analogies to spring mass system
I have just started studying Microphones and Loudspeakers. I need a good text to refer which can explain their mechanical analogies with simplicity and basics too.
2
votes
0answers
90 views
Internal moment in the hull of a pressure vessel
This question is related to the course structural analysis. As part of our exam grade every student has been given different multiple homework assignments which we have to solve.
One of the problems ...
1
vote
0answers
59 views
Limitations on the choice of axis of rotation regarding rolling wheels
Consider a situation where a wheel is rolling without friction on a level surface. Call the center of the wheel $C$, the point where the wheel contacts the ground $G$, and some arbitrary other point ...
25
votes
4answers
9k views
What are the precise statements by Shouryya Ray of particle dynamics problems posed by Newton which this news article claims have been solved?
This recent news article (here is the original, in German) says that
Shouryya Ray, who moved to Germany from India with his family at the age of 12, has baffled scientists and mathematicians by ...
1
vote
2answers
73 views
How can I understand work conceptually?
I'm in a mechanical physics class, and I'm having a hard time understanding what the quantity of work represents. How can I understand it conceptually?
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2answers
179 views
Numerical torque calculation
Suppose I can compute interaction energy of two rigid bodies as a function of their coordinates of centers of masses and Euler rotation angles (total 6 + 6 degrees of freedom). Now I can numerically ...
2
votes
0answers
59 views
Fluid flow in a hollow spring(helix)
Liquid flowing in a long hollow spring(helix). Any effects on the flow rate etc when the spring is stretched or compressed?
When the stretching or compressing of spring is done at brisk speeds the ...
8
votes
1answer
91 views
Are Carnot engine efficieny and Fourier heat trasmission law related?
It just occured to me that the efficiency of Carnot cycles is $\eta= \frac{T_1 - T_2}{T_1}$, that is, the efficiency decreases as the difference between reservoir temperatures decreases. On the other ...
5
votes
5answers
765 views
The Z-Torque: how can it be shown intuitively that it does not work?
There is a new kickstarter project that claims to increase torque and power compared to a normal crank on a bicycle (Z-Torque on kickstarter). If this patented (US Patent Number 5899119) approach ...
0
votes
1answer
99 views
How much (usable) potential energy is stored in a compound bow?
I have done a bit of reading about the energy stored in bows, but I haven't seen anywhere a description of how much energy actually is stored. Clearly there are many factors, bow design being ...
1
vote
2answers
141 views
Total Mechanical Advantage
How do you find the net Mechanical Advantage (MA) of two joint machines. Do you add or multiply the individual MA?
Suppose I have two sets of wheel and axle connected by a fixed pulley. Each of the ...
6
votes
9answers
2k 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 ...
1
vote
1answer
50 views
In which direction is the acceleration directed in a non uniform circular motion?
Acceleration is directed towards the center of the circle in a uniform circular motion. Is it same for the non-uniform circular motion?
8
votes
2answers
223 views
Translation Invariance without Momentum Conservation?
Instead of the actual gravitational force, in which the two masses enter symmetrically, consider something like $$\vec F_{ab} = G\frac{m_a m_b^2}{|\vec r_a - \vec r_b|^2}\hat r_{ab}$$ where $\vec ...
1
vote
0answers
47 views
Fading transition and rotation of and object in 2D
I'm looking for sources about I guess dynamics subject.
The model I'd like to solve is reduced to a question of:
How does a force applied on a certain point of an object results in both fading ...
1
vote
1answer
352 views
Direction of friction on particle placed on a rotating turntable
If a particle is placed on a rotating turntable then the particle has a tendency to slip tangentially with respect to the underneath surface... So the friction should act tangentially to the ...
5
votes
3answers
893 views
Equivalent spring-constant for infinite square grid of springs
Consider an infinite square grid, where each side of a square is a spring following Hooke's law, with spring constant $k$.
What is the relation between the force and displacement between two points? ...
-2
votes
1answer
90 views
Can a bracelet fitted to hand, slip off and stay connected? [closed]
Hello I have a bracelet in my hand with a clip that holds it connected. The bracelete can not slip off my wrist, it is not loose. However while I was standing, it felt from my hand and I found it ...
3
votes
2answers
349 views
Bernoulli's equation and reference frames
So I was thinking about this while driving home the other day.
I've never been quite clear on why when you drive with the windows down air rushes into your car. I thought this might be explained by ...
12
votes
5answers
2k views
Why do rockets have multiple stages?
What is the advantage for rockets to have multiple stages?
Wouldn't a single stage with the same amount of fuel weigh less?
Note I would like a quantitative answer, if possible :-)
0
votes
1answer
172 views
What amount of force is needed to topple a person?
Assuming no sliding and that the shoulder is 1.2m from the feet, what force is required to topple a person weighing 70 Kg standing with his feet spread 0.9 m? If possible, please include an ...
2
votes
7answers
2k views
What are the Constraints on Building a Tower to Space?
When I was a boy I used to daydream about building a tower so tall that the top of it would stick out of the top of Earth's atmosphere project into near space.
There would perhaps be a zero gravity ...
0
votes
1answer
116 views
Speed of sound in air
Quick question. I thought that the speed of sound in air was constant, say in the right conditions of pressure and temperature, and humidity... 300 m/s. Now, if I have a sound source that moves ...
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0answers
22 views
Dual methods in structure optimization
I am studying Structure Optimization, and the teacher took a few weeks to detail dual methods, but I don't get why it is useful.
From an optimization problem with ...
2
votes
1answer
206 views
What variables does the action $S$ depend on?
Action is defined as,
$$S ~=~ \int L(q, q', t) dt,$$
but my question is what variables does $S$ depend on?
Is $S = S(q, t)$ or $S = S(q, q', t)$ where $q' := \frac{dq}{dt}$?
In ...
5
votes
2answers
136 views
Why does motion help you balance on ice skates?
It's almost impossible to balance on a single ice skate if you're standing still. But give yourself just a little forward motion—it doesn't take very much—and it suddenly becomes easy. You can stand ...
1
vote
3answers
795 views
Direction of torque precession of a spinning wheel
Consider a spinning wheel, which is held up by one end of it's axis like this:
To explain why the change of angular momentum is directed as shown in the figure above, one usually says that there is ...
8
votes
3answers
178 views
Is $k_B \rightarrow 0$ the classical limit of stat. mech., as $\hbar \rightarrow 0$ is in QM?
I hear very often among my peers and seniors that just as how $\hbar\rightarrow0$ takes me to classical mechanics from quantum mechanics, $k_B\rightarrow0$ will take me to classical thermodynamics ...
9
votes
5answers
323 views
Driving on snowy roads
'tis the season as they say!
It seems to me obvious that it's better to drive in high gear on snowy roads to reduce the torque.
However, there are completely opposite advices being given on ...
5
votes
2answers
487 views
Ball Rolling in a Parabolic Bowl
I encountered a physics problem which inquired about a ball rolling inside a parabolic bowl (i.e. a bowl where any cross section through the vertex would make a parabolic shape given by $y = kx^2$). ...
1
vote
0answers
79 views
What is the angle of the string with the vertical?
A heavy uniform sphere of radius $a$ has a light inextensible string
attached to a point on its surface. The other end of the string is
fixed to a point on a rough vertical wall. The sphere ...
2
votes
4answers
838 views
Is the Woodward effect real?
Did anyone ever heard about this?I've never seen any serious physicist talk about "mass fluctuations".
Here is the man in his own words http://www.intalek.com/Index/Projects/Research/woodward1.pdf
...
0
votes
2answers
571 views
Mechanical energy problem
Question goes: "An anvil hanging vertically from a long rope in a barn is pulled to the side and raised like a pendulum 1.6 m above its equilibrium position. It then swings to its lowermost point ...
6
votes
1answer
158 views
Can a deformable object “swim” in curved space-time? [duplicate]
Possible Duplicate:
Swimming in Spacetime - apparent conserved quantity violation
It is well known that a deformable object can perform a finite rotation in space by performing deformations ...
1
vote
1answer
90 views
GR limit with massless particles and strong fields
What the mechanics arises if to take limit of general relativity with massless particles interacting with strong fields? Suppose there a system of attracting particles that have zero rest mass. What ...
0
votes
0answers
144 views
Change in time period of pendulum [closed]
A pendulum of effective length $L$ has a bob of radius $R$ filled with water. If the water freezes to ice, what is the change in the time period of the pendulum?
1
vote
1answer
62 views
Diffraction through the slit
In book "Quantum Mechanics and Path Integral", 3-2 Diffraction through the slit:
Under the fig. 3-3, why did Feynman say that we cannot approach the problem by a single application of the ...
4
votes
3answers
156 views
Microgravity: how powerful is an astronaut
In 2008, NASA astronaut Clayton Anderson tossed a 635-kg tank of ammonia coolant overboard from the International Space Station (ISS). Subsequently the tank burned up in earth atmosphere as planned.
...
3
votes
4answers
547 views
“Regular” 20-sided die, vs “life counter” 20-sided die. Same probabilities?
Regular dice are made such that opposite sides of the die add to 1+the number of sides.
For example, a 20-sided die has 14 and 7 opposite of each other, adding to 21.
For certain types of games, ...
0
votes
1answer
70 views
Verify correctness of vintage BASIC drag race phyics simulation? [closed]
I wished to make a more user-friendly version of the vintage BASIC "Drag" program, as seen here, probably in the form of a light-hearted web game:
...
5
votes
1answer
54 views
Fresco in his “Future By Design” introduces drawing of underwater vessel and its front system of generating air bubbles. Is idea energy efficient?
I recently saw Fresco's Future By Design and noticed something miniature to investigate.
My notice regards about one of his illustration he describes in the documentary. Here is the link on youtube, ...
2
votes
3answers
2k views
Torque vs Moment
I was wondering, why in Newtonian physics torque is called "torque" while in static mechanics they call it "moment"?
I prefer by far the term "torque", for not only it sounds strong, but also ...
1
vote
0answers
69 views
How do i choose a motor to power a one cubic metre cement mixer? [closed]
my problem is that I can’t find a way to calculate the power required to drive the shaft and thus decide on a motor, I have tried several times using different methods and calculations but can’t seem ...
6
votes
8answers
4k views
Which Mechanics book is the best for beginner in math major?
I'm a bachelor student majoring in math, and pretty interested in physics. I would like a book to study for classical mechanics, that will prepare me to work through Goldstein's Classical Mechanics. ...
2
votes
1answer
267 views
How accelerometers sense constant velocity movements
There is something I don't understand about accelerometers. I know it's possible to make an Inertial Measurement Unit (IMU) by using "three" accelerometers. So with that, I could calculate the $x$, ...
0
votes
1answer
141 views
By how much will water resistance and upthrust slows down a fully submerged object?
Consider the following example:
While running, I do work and I have a certain velocity and acceleration.
When I'm in a pool (my feet are touching the bottom), I do the same work but, I have less ...
3
votes
0answers
90 views
Obtaining point of application of Ground Reaction Force with use of a hyperstatic load-cell array platform
I'm looking for the theory of an experiment that is giving me a hard time to perform.
I have an instrument composed of a rigid horizontal square plate rigidly supported under each corner by a ...
1
vote
2answers
420 views
Spinning bucket of water in zero gravity
Everyone knows how the surface of a spinning bucket of water would look like on earth - parabolic. But what if we turned off gravity (for instance by doing the experiment in a freely falling lift)? ...
0
votes
2answers
132 views
Why aren't stratospheric balloons compressing their helium to descent?
I can't find a reference of a working stratospheric balloon mounted with a compressor to control its altitude. Is there a big physical difficulty (such as compressor weight/power ratio, or power ...
