If we are concern only with the velocity of the particle along the x-axis, then, this implies that the velocity along the y-axis is hypothetically = 0ms^-1Â
∴ v = (vx=0,vy)Â
vy = 0ms^-1Â
vy = (dr/dt)y = 0ms^-1Â
ry→ = (2ct^2 -dt^3)jÂ
dr/dt = 4ct - 3dt^2
4ct - 3dt^2 = 0Â
4c = 3dtÂ
t = 4c/3dÂ