The equation, of motion of a projectile is y=12x−34x2. The horizontal component of velocity is 3 m/s. Given g = 10 m/s2. What is the range of the projectile ?

y=12x−34x2dydt=12dxdt−32xdxdtor      dydt=12dxdt at x=0or      dydt/dxdt=12 or tan⁡θ=12       ….. (1)Given,      ucos⁡θ=3            ….(3)Now,               R=u2sin⁡2θg=2u2sin⁡θcos⁡θg=2(usin⁡θ)(ucos⁡θ)g=2×3×3610=21.6m