A bar uniformly tapering from a diameter d1 at one end to a diameter d2 at the other end, is subjected to an axial tensile load P. The length of the bar is l and the young’s modulus is E. The extension of the bar is
1
\(\frac{4Pl}{\pi Ed_1d_2}\)
2
\(\frac{PlE}{4\pi d_1d_2}\)
3
\(\frac{Pl}{4\pi Ed_1d_2}\)
4
\(\frac{4Pld_1d_2}{\pi E}\)