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Two persons are holding a rope of neglig...

Two persons are holding a rope of negligible weight tightly at its ends so that is horizontal. A 15kg weight is attached to the mid point which how no longer remains horizontal. The minimum tension required to completely straighten the rope is:

A

15kg

B

`15//2kg`

C

5kg

D

Infinitely large

Text Solution

Verified by Experts

The correct Answer is:
D
When a string is fixed horizontal (by clamping its free ends) and loaded at the middle, then for the equilibrium of point `P`
`2Tsintheta=W` i.e., `T=(W)/(2sintheta)`
Tension in the string will be maximum when `sintheta` is minimum i.e., `theta=0^(@)` or `sintheta=0` and then `T=oo` . However, as every string can bear a maximum finite tension (lesser than breaking strenght). So this situation cannot be realized practically. We conculued that a string can never remain horizontal when loaded at the middle howsoever great the tension be applied.
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Knowledge Check

  • Two persons are holding a rope of negligible weight tightly at its ends so that it is horizontal. A 15kg weight is attached to rope at the midpoint which now no more remains horizontal The minimum tension required to completely straighten the rope is .

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    D
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