The position vector of a aprticle is given as `vecr=(t^2-4t+6)hati+(t^2)hatj`. The time after which the velocity vector and acceleration vector becomes perpendicular to each other is equal to

Options

A. 1 sec
B. 2 sec
C. 1.5 sec
D. Not possible

Answer

A

Explanation

`vec(r)=(t^(2)-4t+6)hat(i)+t^(2)hat(j), vec(v)=(2t-4)hat(i)+2t hat(j)`
`vec(a)=2(hati+hatj)`, when `vec(a) bot vec(v)` then `vec(a).vec(v)=0, t=1 s`