Correct Answer - Option 3 : Correction due to sag and pull
Explanation
The pull or tension which when applied to a tape suspended in the air, equalizes the correction due to pull and sag is known as Normal tension.
Correction due to pull is given by :
\({{\rm{C}}_{\rm{p}}} = \frac{{\left( {{\rm{P}} - {{\rm{P}}_{\rm{o}}}} \right){\rm{L}}}}{{{\rm{AE}}}}\)
Where,
P = Pull applied,
Po = Pull applied at the time of standardization of tape,
L = Length of tape measured,
A = cross-sectional area of tape, and
E = Modulus of elasticity of tape material
Correction due to sag is given by:
\({{\rm{C}}_{\rm{s}}} = \frac{{{{\rm{W}}^2}{\rm{L}}}}{{24{{\rm{P}}^2}}}\)
Equating both the corrections of pull and sag, the value of pull P can be calculated: