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Please........help me out with this question plz......plz.......its little urgent.I have only a doubt what is here normal reaction on hinge means
Q-A uniform rod of length L and mass M is held horizontally with the help of one light vertical string and a hinge as shown.If string is cut suddenly,find out the initial normal reaction on the hinge
Ans-Mg/4

Kaushki , 7 Years ago
Grade 12th pass
anser 1 Answers
Shubham Kumar
take the center of mass as axis of rotation,
the net torque is zero in initial state.
Ta=Tb =>Fa×ra=Fb×rb
here Ta is torque by hinge and Tb is torque by the rope.
ra=rb because the axis of rotation is at the center of the rod.
from this we get our both the forces to be equal.
and the net forces are zero
the forces upward i.e.Fa and Fb are opposed by a force downwards
the only force downwards is mg
Fa +Fb=mg
2Fa=mg   …......from our calculation above.
Fa=mg/2
after cutting the rope the force on right is removed but force on ,left acts as normal reaction and this is equal to mg/2.
 
hope you have understood it well read all the lines  again if any doubt.all the words are important
Last Activity: 7 Years ago
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