A catapult consists of two parallel rubber cords each of length `20cm` and cross-sectional area `5cm^(2)`. When stretched by `8cm`, it can throw a stone of mass `4gm` to a vertical height `5m`, the Young's modulus of elasticity of rubber is `[g = 10m//sec^(2)]`

Explanation

The total elastic potential energy is converted into gravitational potential energy
`(1)/(2) xx (YA e^(2))/(L) = mgh rArr Y = (2mghL)/(Ae^(2))`
`= (4xx10^(-3)xx10xx5xx20xx10^(-2))/(5xx10^(-4)xx(8xx10^(-2))^(2)) = (4xx10^(-2))/(5xx64xx10^(-8))`
`= 1.25xx10^(4) N//m^(2)`