A particle is moving in xy plane and equation of its trajectory is y=120x−3x2 where x and y are in metre. When the distance of the particle from x-axis is maximum, speed of the particle is

When distance from x-axis is maximum, velocity component along y-axis must be zero. i.e. dydt=0 i.e. 120−3×2xdxdt=0⇒dxdt=20xAgain, when y is maximum, dydx=0⇒120−6x=0⇒x=20 m∴ dxdt=2020m/s=1 m/s