Calculate objects Position/acceleration as function of time

[anubis01]

Homework Statement

v_x(t)=a-bt^2
a=4.0 m/s
b=2.0 m/s^2
At t=0 the object is at x=0

a)Calculate objects position as a function of time
b)Calculate objects acceleration as a function of time
c)What is objects maximium positive displacement from the origin

Homework Equations

v_x(t)=a-bt^2

The Attempt at a Solution

a)X_f=x₁ + V₁t + 1/2at^2
X_f=0 + 4(0)+1/2(9.8)(0)^2

c)V₂^2= V₁^2 + 2aD
-V₁^2/2a)=D
-16/-4=4

I'm particularly stumped on question a & b because I'm not quite sure what ithe question is asking and I'm not entirly confident that C is correct. Any help is appreciated.

 

[danago]

You could use the fact that velocity is just the derivative of displacement with respect to time, and then for (b) just recognize that acceleration is the derivative of velocity.