Hi, sorry for the late reply. The reason is, the rigid arm is subjected to only two forces - one at A, and the other at C. So, it is a two-force member. For a two-force member to be in equilibrium, the necessary conditions are (1) the two forces are collinear - act along the line connecting the two points of action, and (2) they are equal in magnitude and opposite in direction. So, in this case, F_A and F_C act along the line AC (at 45 degrees). Hope this answers your query. I have explained two-force members at 39:47. You can join the Google Group groups.google.com/g/nptel-gate-ce-2023-24-naresh for accessing the presentations and resources I use, and also post your doubts and suggestions there. I can also respond faster. :)

Hi Nandhini, sure, but I need your email ID for that. Instead, you can click the link below, log in with your Google account, and click "Join Group". This way, you can join yourself. :) groups.google.com/g/nptel-gate-ce-2023-24-naresh

Yes, I have sent an email to you.

Ok! Got it in the book!

Stiffness factor modification in beam with symmetric loading.

Sure, Shivam. Here it is: indianinstituteofscience-my.sharepoint.com/:b:/g/personal/nareshc_iisc_ac_in/ETm0Uh29Pq9DhEuJv6Z6w5QB320lupgq9zszWr_czjcp4g?e=Xbd9ly The Google sheet is also updated with the video link and solution.