Question

A 1.8-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?

Answer 1

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