Particle moves along vertical axis, position at any time t greater than or equal to 0 is given by the function

,

is centimenters and

is seconds.

a. Find the displacement during the first 6 seconds

b. Find the average velocity during the first 6 seconds

c. Find expressions for velocity and acceleration at time

d. For what values of

is the particle moving downward?

Here are my answers...are they correct? thanks.

a. 12

ok
b. -10

no ... avg v = displacement/time
c.

ok ok
d.

is less than 0? I'm not sure how to do this one..

find the interval where v(t) < 0