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.
2
votes
2answers
130 views
Mechanical work to required battery power
I have a very practical question where I've calculated the mechanical work needed by a simple mechanical system by solving the line integral $W = \int_C \ F \ dx$. However, since I have a black spot ...
2
votes
2answers
113 views
Whats the anti-torque mechanism in horizontal take-off aircraft?
In most helicopters there is the anti-torque tail rotor to prevent the body from spinning in the opposite direction to the main rotor.
What's the equivalent mechanism in horizontal takeoff single ...
2
votes
4answers
457 views
At same level do these two pipe lines give same pressure of water?
Provided that the two pipe lines are of same length, same material and in the same level, is the water pressure in both the layouts same or different?
PS: In 1st pipeline the turns are not ...
2
votes
2answers
299 views
What happens when the string slackens during vertical circular motion?
Consider a particle attached to one end of a string of length $l$ moving anti-clockwise in a vertical circle whose centre is $O$. What exactly happens physically when the string becomes slack and ...
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 ...
2
votes
4answers
79 views
Would a phone move upon vibration in a completely uniform situation?
I was sitting down yesterday and saw my phone vibrate on a side, and it moved about a centimetre per vibration.
I wondered why it moves, and thought perhaps that the side it was on had a slight ...
2
votes
4answers
118 views
Path traced out by a point
While studying uniform circular motion at school, one of my friends asked a question:
"How do I prove that the path traced out by a particle such that an applied force of constant magnitude acts on ...
2
votes
2answers
124 views
Hamiltonian of a water molecule bounded to a surface
Where can I find a way to construct the hamiltonian of a water molecule bounded to a surface? More generally,how can one write the hamiltonian of an atom bounded to a surface?
2
votes
1answer
634 views
Confused with stress, strain and linear thermal expansion
Four rods A, B, C, D of same length and material but of different
radii r, 2r , 3r and 4r respectively are held between two rigid
walls. The temperature of all rods is increased by same ...
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
...
2
votes
1answer
67 views
Why is $dL = L d\epsilon$?
Let's say there's a random elastic material. It's length is $L$ and it's tensile strain $\epsilon= (L-L_0)/L_0$
Now, when one pulls on it the following is true:
$dW_{tot}=FdL =\sigma AdL=\sigma A L ...
2
votes
4answers
204 views
Pseudo force in rotating frames
A bug of mass $m$ crawls out along a radial scratch of a phonographic disc rotating at $\omega$ angular velocity. It travels with constant velocity $v$ with respect to the disc.
What are the forces ...
2
votes
2answers
116 views
distance of electron from proton
An electron is projected, with an initial speed of $1.10 \times 10^5 \text{m/s}$, directly towards a proton that is essentially at rest. If the electron is initially a great distance from the ...
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 $x$, ...
2
votes
3answers
138 views
Effect of surface treatment on fair dice
If I have a perfectly balanced and thus fair cubic die, then polish 3 adjacent faces (so that their coefficient of friction is effectively zero) and roughen the remaining faces (so that their ...
2
votes
1answer
419 views
Force on rope with accelerating mass on pulley
I have a pretty basic pulley problem where I lack the right start.
A child sits on a seat which is held by a rope going to a cable roll (attached to a tree) and back into the kid's hands.
When it ...
2
votes
1answer
241 views
How can you test to see if a dice is weighted?
I was browsing Etsy today and came across this.
What tests are there to see if the dice are usable, ie, if one side isn't favored over another, and if all sides are balanced?
Would this just be to ...
2
votes
2answers
521 views
Stress vs Strain for mild steel
After Yield point on stress strain diagram the under curve occurs what does it mean what will happen for the mild steel at that particular time and again why the curve goes to up and reaches ...
2
votes
2answers
362 views
Wave equations & propagation theories
I'm interrested in making computer simulation but I've run into rather physics oriented problem. I have to choose how to propagate my wave. Though I've found technique called FDTD (finite-difference ...
2
votes
1answer
206 views
significance of maxima and minima of time varying kinetic energy of a system
Consider a system of particles where the kinetic energy of the system is varying with time. I'd like to know the significance (or meaning) of the time derivative of the kinetic energy being zero at a ...
2
votes
1answer
500 views
Does decoherence explain all instances of wave function collapse?
Specifically, how can decoherence explain the appearance of flecks of metallic silver on a photographic plate when exposed to the very weak light of a distant star?
EDIT: Perhaps the advocates of ...
2
votes
2answers
64 views
Hamiltonian of Harmonic Oscillator with Spin Term
We have the usual Hamiltonian for the 1D Harmonic Oscillator:
$\hat{H_{0}}=\frac{\hat{P^2}}{2m} + \frac{1}{2}m \omega \hat{X^2}$
Now a new term has been added to the Hamiltonian, $\hat{H} = ...
2
votes
1answer
138 views
Mechanics question
The following is a question from a past exam paper that I'm working on, as I have an exam coming soon. I would appreciate any help.
A fairground ride takes the form of a hollow, cylinder of radius ...
2
votes
2answers
125 views
Is it possible to control a treadmill's tread speed such that a plane on the treadmill will be prevented from moving?
I've posed the question in this particular way to avoid the ambiguity usually found in the posing of the "airplane on a treadmill" puzzle, e.g.
I'm not specifying how the treadmill is controlled but ...
2
votes
1answer
162 views
Static plane in an inertial frame of reference
Suppose we are given a mechanical frame consisting of two points. How can we prove that assuming any initial conditions there is an inertial frame of reference in which these points will be in a ...
2
votes
1answer
168 views
Is there symmetry in 2d stress tensor in linear elastic fracture mechanics?
Assumptions:
Cross terms in strain tensor are defined as equal $\varepsilon_{xy} = \varepsilon_{yx}$.
pure mode I crack.
Far from crack tip, material is purely elastic and we are way below
yield ...
2
votes
2answers
293 views
Does the potential energy of fluid rising on a string change?
Lets say I have a glass of water at rest. Then I go and hang a string above the water (vertically), such as the end of the string is immersed in the water. Over time some of the water is going to ...
2
votes
2answers
151 views
Movement of a nudged block on a high friction surface
If I apply a single force to an object ‘floating in free space’, then it will either translate (if the force is in line with the Cof G ) or more generally it‘ll rotate about the C of G due to the ...
2
votes
2answers
267 views
a question on Lagrange's equation when the time derivative of the generalized co-ordinates is constant
Consider a system whose generalized co-ordinates are $q_i$ and is under the constraints $\dot{q_i} = K_i \forall i = 1,2,3,...$ where $K_i$ are constants. I have a problem in writing the Lagrange's ...
2
votes
2answers
983 views
Distribution of forces
(little background: I'm trying to develop a small, quick 'n dirty static physics engine to determine whether a stacking of boxes is stable).
If I have a 3D rigid box (with the bottom in the ...
2
votes
2answers
150 views
Cantilever Beam - Maximum Shear of the Beam
A cantilever beam $3\ \text{m}$ long is subjected to a moment of $10\ \text{kNm}$ at the free end. Find the maximum shear of the beam.
The answer is "There is no vertical load, shear is zero"
...
2
votes
1answer
67 views
Atomic physics through classical resonance?
I have a rather general question regarding the theory of Quantum Mechanics. To preface this question, consider a violin string. When a violinist exposes the string to a bow, this is exposing the ...
2
votes
0answers
89 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 ...
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 ...
2
votes
1answer
136 views
Will a precessing spinning whell fall down if there is no friction at all?
If there where no friction at all, would a spinning wheel held up by one end of the axis spin precess forever without falling down?
I just asked another question about the same problem:
Direction ...
2
votes
3answers
573 views
Example in the book: A simple accelerometer
A simple accelerometer
You tape one end of a piece of string to the ceiling light of your car and hang a key with mass m to the other end (Figure 5.7). A protractor taped to the light allows you ...
2
votes
0answers
147 views
Why do control moment gyroscopes exhibit “torque amplification”?
There are a number of articles that describe the benefits of using control moment gyroscopes (CMGs) over reaction wheels in inertial navigation applications. One of the primary benefits of using a CMG ...
2
votes
0answers
75 views
Surface normal on the earth to the sun at a given point in time
How complicated is it to calculate a surface normal on the spherical approximation of the earths surface pointing towards the sun at a given point in time?
What I try do is to highlight a small area ...
2
votes
0answers
141 views
Displacement due to sinusoidal load on a finite strip in an infinite plane
From a paper on tunnel design I've been reading: (http://www.sciencedirect.com/science/article/pii/0886779887900113)
In the present application, the solu-
tion corresponding to a sinusoidal load
...
2
votes
1answer
171 views
How should a closed-ended terrestrial trajectory be corrected for the Coriolis effect?
I have tried verifying the numerical integration of the Coriolis effect for 1000 to 2000-yard rifle fire by switching ON/OFF the Coriolis correction of a good ballistic simulator program (PRODAS). The ...
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vote
6answers
1k views
What will happen if a plane trys to take off whilst on a treadmill?
So this has puzzled me for many a year... I still am no closer to coming to a conclusion, after many arguments that is. I don't think it can, others 100% think it will.
If you have a plane trying to ...
1
vote
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?
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vote
3answers
5k views
What is the difference between a moment and a couple?
In mechanical engineering, the torque due to a couple is given by $\tau = P\times d$, where $\tau$ is the resulting couple, $P~$ is one of the force vectors in the couple and $d$ is the arm of the ...
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)? ...
1
vote
2answers
69 views
What fraction of peak horsepower do typical 4 door passenger vehicles use?
I was surprised when I looked at the power rating of the engine used on a Humvee. It's only ~190 horsepower, which is exceeded by many sedan engines.
So an obvious question is why doesn't my Camry SE ...
1
vote
3answers
429 views
Is it possible to find out the distance traveled by a car if the force applied on it is given?
Say you have car which produces $F$ amount of force which is transferred to the wheels directly.
Now assuming that there is air friction which is causing a retarding force proportional to the ...
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vote
3answers
140 views
What's driving the bucket up?
Just saw this cool video from Plymouth University, which I actually found through Matthen's blog.
They fill a plastic bottle with liquid nitrogen, screw the cap on, drop it in a bucket full of warm ...
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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 ...
1
vote
3answers
508 views
Most elegant/fundamental formulations of the laws of classical mechanics?
Newton tried to do it with three laws/statements. While the first can be derived from the second, the three form a pretty nice framework.
Later on, I've encountered Lagrangian Mechanics, which ...
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?
