A catapult consists of two parallel rubber strings, each of lengths 10 cm and cross-sectional area 10 mm2. When stretched by 5 cm, it can throw a stone of mass 100 g to a vertical height of 25 m. Determine Young's modulus of elasticity of rubber  in ×108N/m2 Take g = 10m/s2

A stretched catapult has elastic potential energy stored in it (elastic potential energy stored in both the rubber strings)           U=12YAl2L×2This energy, when imparted to the stone, it flies off a height 20 m.Energy possessed by the stone = mgh. Now,             U=mgh⇒YAl2L=mgh      Y=mghLAl2=1×10−1×10×25×10−110×10−6×5×10−22∴Y=108 N/m2