Mathematics

Problem

Consider the motion of a particle whose position vector is

\mathbf r(t)=\langle t\sin t,\,t\cos t\rangle

for

0\le t\le 2\pi

. For which of the following values of

t

are the velocity and acceleration vectors perpendicular? a)

t=\dfrac{\pi}{2}

t=1

t=0

t=\pi