Question

A bird sits on a telephone wire.The additional tension produced in the wire is?

Answer 1

If the weight of the bird makes the wire bend with each side of the wire making an angel Ф with the vertical.

Then   2 T CosФ = W        = balancing forces in vertical direction.

           T = W / (2 CosФ)  = W/2   if Ф ≈ 0° or very small.