Is it wrong to tell things like that to your children?
Depends on how smart you were about sneaking math in as something fun and useful.
If the child somehow got to this point, go ahead. It will spare them a lot of headaches.
They use matrix math for that? How did I not know that?! 🤯 I thought they use regular algebra and a bit of trigonometry.
Matrix math is just shorthand for “regular algebra” with a lot of variables
What’s pictured here is the Finite Element Method. Basically, the bridge is composed into little chunks, on which the physics solution is approximated by e.g. linear functions. Then one has to assemble and solve a system of equations (the matrix shown here) to determine the coefficients (i.e. slope) of those linear functions. Putting everything together gives a piecewise-linear approximation of the physics solution, and the smaller you make the chunks the better your solution gets. All of this is of course not done by hand, that’s what computers are for.
Wow that’s crazy, I thought they just drove larger and larger trucks over the bridge until it broke. Then weighing the last truck and rebuilding, apparently isn’t the way it’s done after all.
Nailed it!
The polybridge technique
They need to calculate tolerance and don’t want to break the bridge or lose a truck. They just keep driving bigger trucks until it starts making a weird sound and then they call the limit at that weight.
You don’t really need to do finite element analysis on a truss though. It’s solvable with some simple equations usually. It’s been a long time for me though so maybe I’m wrong
