A string of area of cross-section 4 mm² and length 0.5 is connected with a rigid body of mass 2 kg. The body is rotated in a vertical circular path of radius 0.5 m. The body acquires a speed of 5 m/s at the bottom of the circular path. Strain produced in the string when the body is at the bottom of the circle is ..... x 10^-5 . (Use Young's modulus ${10}^{11} \mathrm{N}/{\mathrm{m}}^2 \mathrm{and} \mathrm{g} = 10 \mathrm{m}/{\mathrm{s}}^{2^{ }}$)