Questions and discussion for this lecture live here. Fire away by hitting Reply below 
Sorry if this question doesn’t make sense but Around 10:20, why did you subtract delta x2 from from delta x1 if the force Fx1 and Fx2 are not same/equal? Again sorry for my poor english.
Hey @Subashs29,
We subtract the delta_x2 from delta_x1 because it’s the displacement at node ‘i’ we’re interested in (when considering the first equation), so we need to remove the influence of the displacement at node ‘j’ since this is captured in the second equation when considering the displacement due to F_x2.
Feel free to follow up if you’re still not clear.
S
Hello Sir,
Continuing from the previous question, I have a follow-up doubt:
If node 1 is subjected to a force F₁, it undergoes a displacement δ₁.
When we write the stiffness equation, why do we subtract δ₂, which is not caused by F₁?
Since δ₂ results from a different force or boundary condition, shouldn’t it be excluded from this particular equation?
Hey @Gopika_Chincholi_Atu - thanks for the question. Seems my original explanation of this hasn’t hit the mark for a few people. Since this is such a foundational concept for everything that follows, I’ve updated the lecture to add an alternative text explanation to the lecture (below the video).
Take a look at that and feel free to follow up with more questions if it’s not clear.
Cheers,
S
Thanks a lot sir!
Really helpful