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Started programming on a ZX spectrum in the 80's and have moved through Assembly, Turbo Pascal, C++, C#, Fortran. My main area of focus is engineering and scientific computing like numerical methods and 3D graphics.


Jun
12
comment Calculating forces efficiently in Lagrangian formalism
Ehm, sketch please.
Jun
12
comment Contra-rotating propellers torques
You know the blade aerodynamics are going to different between the top and and bottom blade so there is going to be an overall yaw trend related to the applied motor torque and lift produced.
Jun
11
comment average speed and velocity
How is speed given in the question and asked for in the answer. Something does not make sense here. Oh, and please show your work when posting question, since this is not a "we do your homework for you" type of website.
Jun
11
comment Static equilibrium question
$A_x = \mu A_y$ leads to $$M (\cot\theta - \mu) = m (\mu - \frac{1}{2} \cot\theta)$$ If $\theta \rightarrow \frac{\pi}{2}$ then a huge amount of friction is needed to keep it stable because or the bottom is going to slide away.
Jun
11
comment Static equilibrium question
I used PowerPoint with a LaTeX add-in called IguanaTex for the labels.
Jun
11
comment Static equilibrium question
First I find the solution for any $A_x$ (rough surface problem). The find the $M$ which makes $A_x = \mu_s A_y$.
Jun
11
answered Static equilibrium question
Jun
11
comment Static equilibrium question
This is exactly what makes this problem so interesting and challenging. It is the treatment of the rope and rod connection that makes all the difference. The question of how the rope tension affects the problem, or simply by splitting the rope in two pieces as suggested would suffice.
Jun
11
comment Static equilibrium question
Imagine a pulley on P. Would the forces on the bar be the same? In this case since the rope can slide past P the tension on the rope is not equal to the reaction force with the bar.
Jun
10
comment Flaring stress in thread relief
Flaring might imply radial growth or radial deformation due to pressure, or it might imply stress due to combustion pressure. Look up merriam-webster.com/dictionary/flaring for more details.
Jun
10
comment Rate of change of a vector
Correct. Since forces and momenta are typically defined in inertial frames, the kinematics must also be viewed on inertial frames for the equations to work out. The last difficulty in this is expressing the mass moment of inertia tensor components in inertial coordinates, when it is defined on body fixed coordinates. See here on how to deal with this.
Jun
10
comment Rate of change of a vector
Did you read: en.wikipedia.org/wiki/Rotating_reference_frame
Jun
10
comment Rate of change of a vector
Your assumptions are correct. You also have to distinguish between changing vector, and changing the components (representation) of a vector. A vector fixed in space will have changing components when viewed from a rotating frame. Conversely a vector fixed on a rotating body will have changing components when viewed from a fixed frame (the $\Omega \times $ part) and non-changing components when viewed from a co-moving frame. In part 2, I talk about non changing components of a rotating vector.
Jun
9
revised Rate of change of a vector
added 828 characters in body
Jun
9
answered Rate of change of a vector
Jun
9
answered Uniform Circular Motion and Centripetal Acceleration
Jun
9
comment Curve of a rod bent by force on both sides
In terms of axial force, the amplitude is $$f^2 \approx \frac{4}{\pi^2} \frac{F \ell^2}{A E}$$.
Jun
9
comment Understanding why a problem was solved a certain way
Yes, you got it.
Jun
9
comment Curve of a rod bent by force on both sides
As an approximation of constant length, the amplitude is found to be $$f^2 = \frac{4 \ell \delta}{\pi^2 }$$ where $\delta$ is the axial displacement.
Jun
9
answered Understanding why a problem was solved a certain way