Differentiate v(t) with respect totto find the acceleration, a(t). The velocity is decreasing if a(t) < 0 and increasing if a(t) > 0. The speed is increasing if either v(t) > 0 and a(t) > 0, or v(t) < 0 and a(t) < 0; it is decreasing if v(t) and a(t) have opposite signs.

To find the position, you need to integrate v(t) with respect tot.