A 20 m steel tape was standardised at a temperature of 30° C under a pull of 5 kg. The tape was used in catenary to fix a distance of 20 m between two points at 40° C under a pull of 10 kg. Young's modulus E=2.1 × 106 kg/cm2, Area = 0.001 cm2, W =0.423 g, coefficient of thermal expansion α = 11× 10-6 /° C. Here to arrive at the total correction (subtractive), the correction for Temperature is calculated using which of the following formulas?
1
\(C_t=\frac{5\alpha(T_m.T_o)}{L}\)
2
\(C_t=\alpha(T_m+T_o)3L\)
3
\(C_t = \alpha(T_m-T_o)L\)
4
\(C_t=\alpha(3T_m-T_o)L\)