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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.


1d
comment Determine reaction forces on square frame
See i.imgur.com/r53xsHo.png
1d
comment Determine reaction forces on square frame
Put B at the origin, and A along the $x$ axis, with the center of the frame also along the $x$ axis. What you drew is incorrect because you are pivoting about the lower left corner. The center of rotation is similar to physics.stackexchange.com/a/88597/392
1d
comment Determine reaction forces on square frame
I put the coordinate system origin where the two sliders intersect. So A has only $x$ axis component, and B only $y$ axis.
1d
comment Determine reaction forces on square frame
$\theta$ is a counter-clockwise rotation of the frame. The higher the $\theta$ the lower B is and the further away A is. You can see this by doing a small angle approximation $$x_A \approx 2 \ell (\theta+1) \\ y_A \approx 2 \ell (1-\theta) $$
Dec
15
answered Tension of 2 massless springs joined together
Dec
15
comment Tension of 2 massless springs joined together
Do sum of the forces where to two springs join to answer your question.
Dec
14
comment Newtons third law and unbreakability
Equal and opposite forces do not imply immobility. You can have motion because the forces are acting on different bodies. See related posts on the side --->
Dec
14
comment Determine reaction forces on square frame
This is a near problem. Converting the two sliders (two degrees of freedom) into a single degree of freedom problem is the key to solving it.
Dec
14
comment Determine reaction forces on square frame
The only thing confusing for me is that a positive $\theta$ is a clockwise rotation which means that a negative torque is needed to increase $\theta$. This makes it difficult to ensure consistency.
Dec
14
revised Determine reaction forces on square frame
added 773 characters in body
Dec
14
comment Determine reaction forces on square frame
It turns out planar kinematics and dynamics are easiest to write down if you just project a 3D problem into a plane (all $z$ values are zero). This makes sure the equations are consistent (instead of doing a 2D cross product).
Dec
14
comment Determine reaction forces on square frame
It is sufficient to just change $m \rightarrow 4m$ you also need to have consistent $I_z$. You need to make the substitution before the value of $I_z = \frac{16}{3} m \ell^2$ is used since it contains the rod mass, and not the net mass.
Dec
14
comment Determine reaction forces on square frame
I have updated the answer. The method was correct, I just assumed a different mass variable.
Dec
14
revised Determine reaction forces on square frame
deleted 49 characters in body
Dec
14
comment Determine reaction forces on square frame
What I did wrong is $m$ which for me is the total mass of the 4 rods. Hence the $I_z$ and $m$ is not correct above.
Dec
13
revised Determine reaction forces on square frame
deleted 11 characters in body
Dec
13
answered Determine reaction forces on square frame
Dec
12
comment Does a bungee cord have a moment of inertia?
Absolutely correct @user44816. You said it much better that I could.
Dec
12
revised Does a bungee cord have a moment of inertia?
added 271 characters in body
Dec
12
answered Does a bungee cord have a moment of inertia?