question_answer

The position of a particle x (in metre) at a time f second is given by the relation \[r=(3t\mathbf{\hat{i}}-{{t}^{2}}\mathbf{\hat{j}}+4\mathbf{\hat{k}}).\]

Calculate the magnitude of velocity of particle after 5s.

A)  3.55 m/s          

B)  5.03 m/s

C)  8.75 m/s          

D)  10.44 m/s