Position of an ant ( S in metres) moving in Y - Z plane is given by...

The velocity of the ant can be found as follows:

\begin{cases}\overset{\to}{v} & = & \dfrac{d\overset{\to}{S}}{dt} \\ & = & \dfrac{d}{dt}\left(2{t}^{2}\overset{^}{j} + 5\overset{^}{k}\right) \\ & = & 4t\overset{^}{j} . . . \left(1\right)\end{cases}

At $t = 1s$, from equation (1), it follows that

\overset{\to}{v} = 4\overset{^}{j}