How Do You Calculate Total Displacement in Multi-Stage Motion Problems?

[TheGeek]

Homework Statement

A). A particle starts from rest and moves for 10 s with an acceleration of 2 m/s^2.
B). For the next 20 s, the acceleration of the particle is -1.2 m/s^2.
C). What is the displacement of the particle at the end of the 30 s.

2. Homework Equations
Kinematic equations

The Attempt at a Solution

I was able to find the Displacement of A = 100 m and B = 20 m
However I can't find the Displacement of C because I don't know how to find the last acceleration or V-final

Thank You.

 

[jedishrfu]

Draw a graph of the motion and from there you can see how to get the answer.

From part B you can get the velocity needed for part C. Remember vf=at+v0 where v0 is from part A

 

[haruspex]

B = 20 m

How did you get that?

From part B you can get the velocity needed for part C

Did you mean "From part A you can get the velocity needed for part B"?

 

[jedishrfu]

Yes, it's a chained problem right? So the results of A with $v_{Afinal}$ and $d_{Afinal}$ are inputs to part B. and the results of $v_{Bfinal}$ and $d_{Bfinal}$ are inputs to C.