A closecoiled helical spring is subjected to an axial pull of W. The spring is made out of d mm diameter rod and has n complete coils each of radius R and modulus of rigidity as N then the deflection under the pull is
1
\(\delta\) = \(16WR^3n\over Nd^4\)
2
\(\delta\) = \(32WR^3n\over Nd^4\)
3
\(\delta\) = \(64WR^3n\over Nd^4\)
4
\(\delta\) = \(64WR^2n\over Nd^3\)