Mechanical Engineering: Ch 13: Virtual Work Applications (7 of 39) Completely Constraint Structure**

[@ull893]

Thank you. I'm broke otherwise I would have donated to your channel. Such a great teacher is hard to find in real life ! Only on virtual world they exist.

[@wakasukku]

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[@martimfreitas1554]

@@wakasukku so i am not alone with tests abut virtual work right now...

[@832aftab]

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[@HeroDesigner]

Hello sir, you have made a mistake while multipleyinf F force with dy, there is a negatif sign before L.sin(teta).d(teta)

[@HumanKDas]

is that wrong or we are not getting it ??

[@martimfreitas1554]

it is not a mistake, we use the absolute value of dy

[@antoniotonisi2419]

Thank you professor. You made this subject more clear to me. One more subscriber.

[@MichelvanBiezen]

Thank you. Welcome to the channel! 🙂

[@NKShahariar]

hello sir, I have a question Why are we ignoring the minus sign while er are pluggin in the value of dy?

[@MichelvanBiezen]

If you only want the magnitude of dy, then the negative sign is not needed. If you want to include the negative sign, then you must also add a negative sign in the equation relating x to y (as y decreases, x increases).

[@nellvincervantes3223]

dy is negative because it is directed downward also the force F pointing downward thats why negative times negative is positive. Am I right sir biezen

[@not_ujju]

Actually a.b=|a| |b| cos(angle)

[@princewillagada]

Watched the video this morning. Same question came out in exam 😊😮. Thanks you

[@MichelvanBiezen]

Great 👍

[@alexdowad947]

I have a question about the method used in this video. Since the structure is completely constrained, and is not really moving in any direction, why is it valid to (arbitrarily) decide that the virtual displacement vector at point B should point to the right? Wouldn't it be equally valid to imagine it as pointing down, or in some other direction? And if we did so, wouldn't the calculated forces on the structure come out differently? Or did we treat it as pointing to the right because we wanted to know what force the structure will experience along the horizontal axis, and not the vertical axis?

[@MichelvanBiezen]

It depends on how the structure is constrained and what the expected motion is.

[@raulmuresan456]

Would it be possible to then find the value of theta at equilibrium?

[@m.l.v.wijesiri3076]

why didn't you consider the negative sign of dy professor?

[@MichelvanBiezen]

Since the displacement in y is in the same direction as the force applied the work done is positive.

[@bandlelihledee3669]

ay ay ay nkabi u minus sin u shonaphi?