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.
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2answers
266 views
Angular Momentum and Force
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 ...
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1answer
37 views
Finding the coffecient of restitution
A ball moving with velocity $1 \hat i \ ms^{-1}$ and collides with a friction less wall, afetr collision the velocity of ball becomes $1/2 \hat j \ ms^{-1}$. Find the coefficient of restitution ...
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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?
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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 ...
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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 ...
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3answers
796 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 ...
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2answers
74 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 ...
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1answer
373 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 ...
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2answers
500 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 ...
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4answers
327 views
Will tensile strength keep a cable from snapping indefinitely?
Trying to secure a wall hanging using magnets; me and a coworker came up with an interesting question:
When the hanging is hung using 1 magnet, the weight of it causes it to quickly drag the ...
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2answers
1k 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? ...
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1answer
50 views
How large of a solar sail would be needed to travel to mars in under a year?
I'm attempting to approach this using the identity
$$F/A = I/c$$
I can solve for Area easily enough
$$A = F(c/I)$$
and I know the distance $d$ is
$$d=1/2(at^2)$$
But I'm having difficulty trying to ...
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1answer
49 views
Floating Objects and Weight
The Situation:
A ball is placed in a beaker filled with water and floats. It is also attached to the bottom of the beaker via a string.
The Question:
The ball is attached to the beaker, thus ...
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1answer
64 views
Lego Blender and gear ratios
I bought the Lego Kit LEGO Crazy Contraptions. It allows the learner to build a blender. My son, the engineer, said something to our grandson, his son, about a gear ratio. Can someone translate?
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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 ...
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1answer
193 views
Euler's buckling formula applicable for impact calculations?
$$F = \frac{\pi^2 EI}{(KL)^2}$$
Is Euler's buckling formula applicable for impact calculations, considering speeds relevant for a car or aircraft crash?
If there is a level where the formula ...
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1answer
363 views
Classical Mechanics for Mathematician [duplicate]
Possible Duplicate:
Which Mechanics book is the best for beginner in math major?
I am looking for suitable ways to learn mechanics in mathematician's perspective.
I went through:
...
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1answer
83 views
How to find the value of the parameter $a$ in this transfer function?
I am given a transfer function of a second-order system as:
$$G(s)=\frac{a}{s^{2}+4s+a}$$
and I need to find the value of the parameter $a$ that will make the damping coefficient $\zeta=.7$. I am not ...
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2answers
264 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 ...
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1answer
232 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 ...
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1answer
167 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 ...
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2answers
280 views
What, if anything, makes forces the “cause” and acceleration the “effect”? [closed]
We typically say that forces cause acceleration inversely proportionate to mass. Would it be any less correct to say that acceleration causes forces proportionate to mass? Why?
(Note that the ...
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1answer
270 views
Lagrangian density of linear elastic solid
I need the general expression for the lagrangian density of a linear elastic solid. I haven't been able to find this anywhere. Thanks.
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1answer
329 views
Cheetah prosthesis efficiency
I want to compare the much-talked about Cheeta running prosthesis to a the normal running process in terms of force and energy, but I don't know where to start. How would you start the comparison? A ...
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1answer
686 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 N*m.
Each (of the 3) propeller props weighs approximately 45 Kg and has a Moment of ...
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1answer
31 views
Mechanical shock resistance as a function of shape
I have a system where I'm dropping glass tubes filled with some sample from a certain height, along a track. I can apply a back-pressure of air to push them down faster, and in general the faster they ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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1answer
84 views
Why can we analyse force balance on a dislocation?
Dislocation (like screw or edge dislocation) is not a 'real' thing, while Newton's laws only apply to a real object (no matter macroscopic, like stars, or microscopic, like atoms).
In the derivation ...
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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 ...
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2answers
70 views
Mechanics Energy (Calculus)
A particle moves with force
$$F(x) = -kx +\frac{kx^3}{A^2}$$
Where k and A are positive constants.
if $KE_o$ at x = 0 is $T_0$ what is the total energy of the system?
$$ \Delta\ KE(x) + \Delta\ ...
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0answers
155 views
moment of tennis racket & volley
I've been looking for the relation between moment of a tennis racket and its maneuverability. If I define maneuverability as the easiness to get in position for quick reaction strokes like volleys and ...
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0answers
88 views
Is there analysis library for stress-strain data?
I have three column data that has time-displacement-force from 1D tensile/compression test. Now I would like to get the standard mechanical properties of the material, like Young modulus, yield ...
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1answer
209 views
How to find the value of the parameter a in this transfer function? [duplicate]
Possible Duplicate:
How to find the value of the parameter $a$ in this transfer function?
I am given a transfer function of a second-order system as:
$$G(s)=\frac{a}{s^{2}+4s+a}$$
and I ...
1
vote
0answers
238 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 ...
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0answers
164 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 ...
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0answers
135 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 ...
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0answers
123 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 ...
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0answers
142 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 ...
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0answers
110 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?
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1answer
445 views
How to determine velocity and mass of asteroid 2011 CQ1
As you may have seen, a small asteroid had a near miss with the earth a few days ago.
As a physics teacher teaching momentum, I think this could be an excellent problem for my students, however, I ...
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2answers
155 views
Is there any case in physics where the equations of motion depend on high time derivatives of the position?
For example if the force on a particle is of the form $ \mathbf F = \mathbf F(\mathbf r, \dot{\mathbf r}, \ddot{\mathbf r}, \dddot{\mathbf r}) $, then the equation of motion would be a third order ...
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3answers
165 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 ...
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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. ...
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2answers
338 views
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?
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3answers
677 views
4th equation of motion
Ive been given the 4 equations of motions The fourth being:
$$s=ut+\frac{1}{2}at^2$$
If rearranged it forms the quadratic equation
$$at^2+2ut-2s=0$$
But that means that t has 2 values.
Will ...
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1answer
710 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 ...
