A1.8-kg object moves in the x direction according to the following function:
x(t) = 2t2 + 3t − 5
(si units). what is the force on the object after 2.7 s?

Well, if the position is    x(t)  =  2t² + 3t - 5

then the speed is          x ' (t)  =  4t + 3    (first derivative of  'x'  wrt  't')

and the acceleration is     x ' ' (t)  =  4      (second derivative of  'x'  wrt  't')

Apparently, then, the acceleration is constant, and is not a function of time.

After 2.7 seconds or 2.7 years, the acceleration is  4 .

Force = (mass) x (acceleration)

Force =  (1.8)    x      (4)

Force =            7.2 newtons