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I've drawn an FBD of one leg of the table the picture. I've a feeling I'm missing something. Am I?

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  • $\begingroup$ Yes there is a sideways friction force on the floor $\endgroup$ – joojaa Sep 23 '18 at 11:15
  • $\begingroup$ Thanks for the reply. Yes, there can be. But I've decided to ignore it. $\endgroup$ – gaurav Sep 23 '18 at 11:40
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    $\begingroup$ you wont get the right answer if you ignore it $\endgroup$ – joojaa Sep 23 '18 at 12:46
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    $\begingroup$ If you ignore the floor friction, this is a terrible design for a table because it will collapse if you put an off-center load on it. Basically it's a en.wikipedia.org/wiki/Four-bar_linkage $\endgroup$ – alephzero Sep 23 '18 at 21:09
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Your FBD is correct if we assume the legs are on a roller or the floor is very slippery and or if your table legs have received a few jerks enough to slide open to a relaxed position releasing the friction force.

otherwise the forces on the leg are indeterminate depending on the friction coefficient and the original base length the table is placed on the floor. Because the cable can not have compression stress the legs can be randomly positioned in different angles and $ friction= \mu\times sin\alpha \times weight$ will be different. Alpha is the angle of leg with floor, and meu the friction coefficient.

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