Physics

Problem

The velocity of a particle is given by

\mathbf v(t)=\bigl(4t\,\text{i}-3t^{2}\,\text{j}+6\,\text{k}\bigr)\,\text{m s}^{-1}

. Find its instantaneous speed at

t=2\,\text{s}

. a)

20.0\,\text{m s}^{-1}

15.6\,\text{m s}^{-1}

14.4\,\text{m s}^{-1}

18.8\,\text{m s}^{-1}