A car starts from rest and accelerates at 5 m/s^2 for 4 s, then maintains that velocity for 3 seconds, then decelerates at the rate of 2m/s^2 for 3 seconds.

Question

A car starts from rest and accelerates at 5 m/s^2 for 4 s, then maintains that velocity for 3 seconds, then decelerates at the rate of 2m/s^2 for 3 seconds. 
a) what is the final speed of the car?
b) how far does the car travel?

a) v = v_0 +at
=0+2(3)= 6m/s
Would I use the part of the question where the car decelerates to 2 m/s for 3 s? Or would t=10s and a=2m/s^s?

b) d= 1/2at^2
=1/2 (6)(10)^2
=1/2(600)
=300m
I got 6m/s^2 as the acceleration from question a)
Is this correct?

bobpursley · Answer

a) find the first acceleration: vf=vo+at= 5*4= 20m/s, then it slows vf=20m/s-2*3= 14m/s how far: break it up into three parts again, and solve.