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**Position and acceleration vector -- parallel and perpendicular**

## Homework Statement

The motion of a particle is defined by the position vector

r = A(Cos t + t Sin t) i + A(Sin t + t Cos t) j where t is expressed in seconds. Determine the values of t for which the position vector and acceleration vector are

a) perpendicular

b) parallel

## Homework Equations

## The Attempt at a Solution

For acceleration i have differentiate r twice and arrive at the equation. So, i should go for cross product to find 't' when they are parallel and dot product when they are perpendicular.

Am I right in my procedure, revered members?