5.27. a)
We know that after the block has reached terminal velocity (when it has fallen more than .5 m), that the acceleration is zero. Therefore, we can find the constant c.
a = g - c v = 0
Also, since the styrofoam falls 1.5 m at constant speed in t = 5s,
then we can find the terminal velocity, 
.
Therefore, the constant c is given by
b)
Pluggin in zero for the velocity, or by reasoning we can see that the acceleration of the styrofoam when we just release the block at t=0 is zero.
c)
When v = .15 m/s,
in the negative y direction.