Mathematics

Problem

A body moves along a straight line with displacement

x = t^{3} - 6t^{2} + 9t

(metres). Let

v_{1}

and

v_{5}

be its instantaneous velocities at

t = 1\,\text{s}

and

t = 5\,\text{s}

respectively. Which option is correct? a)

v_{1}=-6\,\text{m s}^{-1}

v_{5}=18\,\text{m s}^{-1}

v_{1}=0\,\text{m s}^{-1}

v_{5}=24\,\text{m s}^{-1}

v_{1}=0\,\text{m s}^{-1}

v_{5}=15\,\text{m s}^{-1}

v_{1}=4\,\text{m s}^{-1}

v_{5}=20\,\text{m s}^{-1}