A ball is projected from the origin. The x- and y-coordinates of its displacement are given by x=3t and y=4t−5t2 . Find the velocity of projection (in ms-1).
vx=dxdt=3 and vy=dydt=4−10t=4−10(0)=4
v=vx2+vy21/2=32+421/2=5ms−1