Position and time interval of a particle

[mrssmth]

Homework Statement

The position of a particle moving along the y-axis has a position given by y = 0.20m + (8.0m/s) t - (10 m/s2) t2. is there any time interval during which the particle is not moving?

Homework Equations

The Attempt at a Solution

I said No but I'm not sure why exactly it is never moving.

 

[rl.bhat]

There is one instant when the particle is not moving. Find dy/dt and equate it to zero to get that instant.