A load of `1kg` weight is attacheed to one end of a steel wire of cross sectional area `3mm^(2)` and Young's modulus `10^(11) N//m^(2)`. The other end is suspended vertically form a hook on a wall, then load is pulled horizonatally and relased. When the load passes through its lowest position the fractional change in length is `(g = 10m//s^(2))`

Options

A. `10^(-4)`
B. `10^(-3)`
C. `10^(3)`
D. `10^(4)`

Answer

A

Explanation

`e = (T)/(A) (l)/(Y), mg l = (1)/(2) mv^(2), T = (mv^(2))/(l) + mg`