A horizontal bar has mass 5 kg, length 0.30 m and has a mass M at one end as shown in the accompanying schematic sketch. A cable is attached at point A, 0.05 m from the pivot point (fulcrum) P and its other end makes a negligible angle with the a rod joined to the pivot P. The top end of the rod is fixed to the roof. The maximum tension the cable can withstand is 1050 N. Then which force act at pivot and How is: The maximum value of the normal component of the force at the pivot is 850 N and what will be the the maximum value of the horizontal component of the force at the pivot?

First i have calculated the maximum mass of object M which came out to be 15 kg. Taking Tcos∅= T.( ∅ is the angle between rod and cable). But i don't know the angle cable is making and am confused how to proceed solving this question. I don't have a clear idea how which acting will have components at pivot? If Tcos∅ = T then normal component will also be equal to 1050 N but in answer it says its not. Confused what will be the normal component of force at pivot??

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  • $\begingroup$ This looks like a homework question, so just a hint about the angle you don't know. The question says the angle between the cable and the rod is "negligible". $\endgroup$ – Dr Chuck Jan 18 '18 at 7:28
  • $\begingroup$ Yes thats why I took Tcos∅= T and normal component is also equal to Tcos∅ right? Then Normal component of force must also be equal to 1050N. But answers says its 850N don't know how $\endgroup$ – user522338 Jan 18 '18 at 7:32
  • $\begingroup$ Sorry, I misread what you wrote. $\endgroup$ – Dr Chuck Jan 18 '18 at 12:36

Just assume a force upwards/downwards(as its a rod) from the pivot and equate upwards forces to downward forces. You should get the pivot force with sign convention.

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