Question

The position s of a point (in feet) is given as a function of time t (in seconds).

s = −10 + t − 15t2;  t = 8

(a) Find the point's acceleration as a function of t.

s''(t)=

I know this answer, it is -30

(b) Find the point's acceleration at the specified time.

s''(8) = I don't know this one

Answer 1

s = -10 + t - 15t^2
s' = v = 1 - 30t
s'' = a = -30 , which is a constant

so no matter what value of t you take, e.g. t = 30
there is no variable to sub into, so

a = -30