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Using 2 light cords a bob is held in equilibrium at A. The horizontal cord is cut and the bob is allowed to swing as a pendulum. Calculate the ratio of the tension of the supporting cord in position B to that in position A.

Using 2 light cords a bob is held in equilibrium at A. The horizontal cord is cut and the bob is allowed to swing as a pendulum. Calculate the ratio of the tension of the supporting cord in position B to that in position A.
 

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Grade:11

7 Answers

Neeti
571 Points
8 years ago
Finally.
See in the first case when the cord has no been cut, and the bob is in equilibrium, therefore, Tacos\Theta = mg (equilibium in vertical direction ) and Ta sin \Theta = F ( equilibirum in horizontal direction) .
Squaring and adding the two equations we get Ta = (F2 + (mg)2)1/2 
 
Now when the string is cut and the bob starts oscillating, at the extreme positing B ( assuming it to be exteme since \Theta same for positions A and B and and oscillation starts at A so it is considered to be one extreme position so B is the other extreme) 
 
For position B, there is no force is radial direction since body is momentarily at rest, So only centripetal = mv2/l = Tb -mgcos\Theta 
So Tb = mgcos\Theta + mv2/l 
 
But i’m not sure if this is the correct but this is the only answer i could get.
But try solving it, try to simplify it a little. That might help.
Raisinten
12 Points
8 years ago
I liked your working but the answer is (cos@)^2
Neeti
571 Points
8 years ago
I’m sure you’ll somehow get it from the equations i derived. Because there’s no other way to solve it i guess. sorry i couldn’t get the answer, it just needs to be simplied. 
Raisinten
12 Points
8 years ago
Do you know anyone who might be able to solve 
Neeti
571 Points
8 years ago
Well you can wait, some other askiitian tutor might. 
But what about your physics teacher? In school or coaching?
Raisinten
12 Points
8 years ago
I have no tutor and my physics teacher won’t answer it as they haven’t started the chapter.
Neeti
571 Points
8 years ago
Well that is a weird physics teacher. Do one thing, post the question again, you may have to wait for some time , you’ll hopefully get another answer from another tutor :) I’ll try this question again, i just hope i’m able to solve it and i’ll get back to you ASAP :)

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