When is speed increasing in curved motion?

[isukatphysics69]

Homework Statement

When if ever is the speed of the object increasing?

Homework Equations

Dot product result, cos(theta) acceleration perpendicular, acceleration parralel

The Attempt at a Solution

I solved the problems first three parts and found when the objects speed is constant using the dot product, now i am trying to figure out how to find if it is increasing. Is it when a(parrelel)*cos(theta) = 0? i have my result from the dot product as 2t^3+6t^2-8t. i set it equal to 0 to find when speed is constant and got t=-4,t=1,t=0. Now i need to find speed increasing and am not sure exactly

 

[isukatphysics69]

I FIGURED IT OUT!!