A particle P moves such that its position vector r with respect to the origin O at the time t is given by
r = cos3ti + sin3tj
a) Find an expression for v, the velocity of P at time t.
b) Show that the direction of v is perpendicular to that of r for all values of t.
c) Find the speed of P.
OK for part a I'm assuming you differentiate r which i get
v = -3sin3ti + 3cos3tj
is this correct??Part b Im stumped with, not sure I've learned that.
For part c i think maybe i use equation v=u+at ??
if so how could i find t ?