please tell me how to solve this one

two personsare holding a massless ropetightly at its ends so that it is horizontal. a 15 kg weight is attached at its midpt which now no longer horizontal. the min tension required to completely straighten the rope is-(ans-infinite)

Hi Zahid,

Let alpha be the angle which the rope is making with the vertical when weight is attached at its mid-point.

let the tension in the rope be T.

The 2Tcos(alpha) = mg ( by using Force balance in vertical direction for the weight )

 T = mg/(2*cos(alpha))

Now when the rope is straight then , alpha is 90 degrees.

cos(alpha) = cos(90 degree) = 0

T = mg/( 0 ) = Infinite

Please feel free to ask as many questions you have.

Puneet