Proof: Velocity and acceleration are always perpendicular

[whizvish]

Hi.
I was wondering if there was a proof to show that Velocity and Acceleration are always perpendicular, when a particle moves on a curve R(t) with constant speed.

Thanks in Advance.

 

[xXAceFireXx]

r' (dot) r'' = 0

prove that and thats enough proof that they are perpendicular