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
1answer
683 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 ...
0
votes
1answer
242 views
Why is the optimum wheel size of a bicycle about the same as that of a car?
The optimum wheel diameter of cars and bikes appear to be roughly the same, certainly well within an order of magnitude. This is despite very different average speeds and propulsion mechanisms.
Can ...
1
vote
2answers
75 views
Acceleration: Value Disparity?
If we consider a ball moving at an acceleration of $5ms^{-2}$, over a time of 4 seconds, the distance covered by the ball in the first second is $5m$. In the 2nd second will $5 + 5 = 10m$. In the ...
5
votes
1answer
173 views
Does a straight water hose issue water at a greater pressure than a Coiled water hose of same diameter and length?
I have a one BHP water pump, the water pressure of a coiled hose connected to the water pump output side was not that great. Would an unwound water hose produce greater water pressure? [Friction ...
1
vote
0answers
245 views
How equivalent are heat energy and work energy in connection with a spinning flywheel?
Let's say we have two identical spinning flywheels, that have arbitrary geometry, and are made of copper.
Now we apply some heat energy at the center point of flywheel A, causing it to slow down a ...
3
votes
0answers
120 views
Symmetries of separable potential
For separable potential, say $x^4+y^4$, its symmetry are degenerate.
Is that a generic case to every separable potential? I will explain my question:
The potential $x^4+y^4$ has $A_1, B_1, A_2, B_2, ...
1
vote
0answers
173 views
Exam review question on thermodynamics [closed]
A cube has a side length of $20\text{ cm}$.
An atom in the gas moves around the cube as shown.
It continually bounces off the four lateral walls of the cube.
The atom has a mass of $6.6\times ...
2
votes
1answer
167 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
174 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 ...
0
votes
1answer
775 views
Speed of a fly inside a car
A couple of weeks ago I was travelling in a car (120 km/h approximately) and I saw a fly flying in front of me (inside the car, near my nose, windows closed). I wonder how was that possible.
Does it ...
0
votes
0answers
113 views
Dynamo-meter and forces problem [closed]
I have this system:
Where D stands for dynamo-meter, and you can exclude all lines\dynamo-meters\balls weight and friction.
The left ball connects to body A, and the right ball connets to the wall.
...
0
votes
2answers
812 views
Calculation of the maximum load to the bar
Looking for a way of calculating the maximum weight (W) to the rod with the given length (L) where the rod did not break and that only bend for (b) mm.
Need only approximative solution (read: ...
2
votes
0answers
155 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 ...
0
votes
2answers
1k views
Work done by spring over distance
I'm working through a problem involving energy conservation. Unfortunately, I cannot calculate the work done by a spring.
...
5
votes
1answer
137 views
Distance a curveball travels?
I've seen some discussions regarding the movement of a spinning object, say a curveball. However, all have been largely qualitative. I was wondering if anyone has seen or worked through a ...
2
votes
2answers
303 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 ...
1
vote
1answer
390 views
Conjugate Variables and Fourier Transforms in Classical Physics
Let q be a generalized coordinate with a conjugate momentum p and a potential resulting in a periodic motion of q. What is the meaning of the Fourier transform of q(t) over its period? Can this be ...
0
votes
0answers
36 views
Trace the path for the following case [closed]
2 identical balls 1m apart are moving in such a way that they are rotation around each other with same speed.
Trace the path followed by them.
0
votes
1answer
111 views
Determine the tensor of contraint and deformation of a cube under compression
We have a cube under compression with dimension l1*l2*l3, is put between 2 rigid plates in the axis 1 (two plates block the deformation of the cube in thí axis), the cube is also put on a rigid plate, ...
1
vote
2answers
269 views
Spin angular momentum of a system of particles : Is there any energy associated with it?
Consider a system of point particles , where the mass of particle $i$ is $μ_i$ and its position vector is $\vec{r}_i$. Let $\vec{r}_\text{cm}$ is the position vector of the center of mass of the ...
1
vote
2answers
506 views
What are the expressions for rotational and translational kinetic energies of a system of point particles?
Consider a system of point particles , where the mass of particle $i$ is $\mu_i$ and its position vector is $r_i$. What are the expressions for translational kinetic energy and rotational kinetic ...
1
vote
3answers
84 views
I think there is something wrong with this problem. How do you know if the vertical acceleration is zero?
Suppose a block with mass 3kg is on a frictionless table and a force of 15N pulls it from an angle of 38 degrees above the horizontal.
1) What is the apparent weight of the block?
2) What is the ...
0
votes
0answers
716 views
Studying from “Berkeley Physics Course Volume I - Mechanics”
I'm a first year physics student and the main source for our Physics I course is "Berkeley Physics Course - Volume I."
I'm having a hard time understanding this book because it assumes a pretty high ...
4
votes
3answers
290 views
Calculating stress without strain
I am working on an algorithm for a real-time simulation.
I would like to calculate to extremely permissive tolerances approximate values for the stress within a 2D geometry. It will not be difficult ...
0
votes
3answers
166 views
Do we know how matter moves matter?
I was surprised when reading an apologetics book recently that attempted a rebuttal of the claim that "An immaterial mind cannot interact with the physical order." Here was the response:
How could ...
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 ...
7
votes
2answers
516 views
How fast does force propagate through matter? [duplicate]
Possible Duplicate:
Is it possible for information to be transmitted faster than light?
Consider the following thought experiment. You have a long perfectly rigid beam (for the sake of ...
1
vote
1answer
233 views
centrifugal force in static frame of reference
The other day we derived Kepler's third law.
$$
\left( \frac{T_1}{T_2} \right)^2 = \left( \frac{r_1}{r_2} \right) ^3
$$
In order to derive this, you can look at a given planet that revolves around ...
1
vote
0answers
143 views
Error caused by pulley eccentricity [closed]
Not sure if this is perfectly a physics question:
A rope is wrapped around a cylinder of diameter D. The cylinder is slightly eccentric so that the distance between the axis of the cylinder and the ...
3
votes
0answers
153 views
Does a thermally expanding torus experience internal stress?
I'm trying to learn continuum mechanics and thermo-mechanics.
As we know, heating an object increases the mean atomic distance $a_0$ of the atoms in a rigid body. Let's assume it is a linear elastic ...
4
votes
2answers
372 views
Is instantaneous velocity an abstraction?
In introductory analysis, the discussion the derivative emphasizes that while average rates of change are measurable, instantaneous rates of change are a "limiting abstraction". While this makes ...
0
votes
3answers
3k views
Yield Strength versus Ultimate Strength
What is the qualitative difference between these two:
As seen on the table Typical yield and ultimate strengths.
I am trying to resolve the meaning of the phrase "contact yield stress" from C. ...
2
votes
1answer
441 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
256 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
153 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 ...
3
votes
2answers
363 views
What is the mathematical formulation for buckling?
Argument: Buckling is an engineering concept that can only be applied to thin columns with compressive loading.
(Is it possible to) Prove the above sentence right or wrong with mathematical ...
1
vote
0answers
125 views
Conveyor scales modeling
Assume we have a conveyor scales. Which consists of scales, and motor with conveyor belt placed above, so that the boxes can be measured (weight) while moving above. What I want is to create the model ...
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
146 views
Flattening rate of a parabola
If you have a piece of paper that is furled and unfurled so that it's in the shape of part of a parabola, and knowing that if you leave it, it'll flatten itself after time, would it flatten faster if ...
0
votes
1answer
703 views
Is the static gauge pressure of a free jet always atmospheric?
Let's say I have a free jet of air leaving a pipe into the atmosphere. I know that the static gauge pressure at the pipe exit is equal to the atmospheric. But what about the static gauge pressure 10 ...
1
vote
1answer
172 views
Is the pressure at the outer hole on a pitot static tube equal to atmospheric pressure?
I'm looking at a pitot static tube question right now and I just need some clarification. There is the outer hole on the pitot static tube, not the hole that the air stream goes through, but the other ...
1
vote
0answers
112 views
How do I determine where the maximum air velocity around an object is?
I have a freestream of air directed at an object. Is there a way to find where the maximum air velcoty occurs with only having initial air speed and static pressure at the object?
3
votes
1answer
548 views
What phrases describe collisions with coefficients of restitution less than zero or greater than one?
The coefficient of restitution describes the elasticity of a collision:
1 = perfectly elastic, kinetic energy is conserved
0 = perfectly inelastic, the objects move at the same speed post impact
...
0
votes
1answer
71 views
How must you spin the ball to make it alternate between 2 positions? [closed]
Assume any parameters you may need. Thanks in advance.
2
votes
3answers
680 views
Initial vs Constant Orbital Velocity
I am working on some basic physics simulation for a game and need to simulate gravity. I have a system working that is behaving more or less correctly so far, but I want to see if I can send a ...
0
votes
1answer
129 views
Is pressure distribution affected by shape
We have two iron (assume real-life stiffness) manhole covers resting on friction-less, perfectly smooth shims on flat ground. One is circular and the other square.
If a force F is applied vertically ...
0
votes
1answer
80 views
Explain moving lightbulb [closed]
An acquaintance of mine, while being home alone, saw that the light bulb in the room which was hanging from the ceiling with wires having a pendulum motion which was more than noticeable. He says that ...
6
votes
2answers
259 views
How does the distance between two rails effect the speed of a steel ball bearing?
As part of a school science project, I constructed a Rollercoaster using Polyurethane tubing as rails for a steel ball bearing to rest on. In the process of building the coaster I observed that ...
2
votes
1answer
211 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 ...
0
votes
0answers
476 views
Physics tension question [closed]
Two blocks are pulled across a frictionless surface by a $240\ N$ force, as shown in the diagram below: $60\ kg$ - - - cord - - - $20\ kg$ → $240\ N$. If the blocks are accelerating at $3\ m/s^2$ what ...
