Quick Physics Help?

Question

I need help with the following problem, and it would help if you could break down the steps for me so I can follow along. I also need to know if the car is decelerating or accelerating as well. Any help is appreciated, thanks!

A car is traveling to the left, which is the negative direction. The direction of travel remains the same throughout this problem. The car's initial speed is 27.0 m/s, and during a 5.1 s interval, it changes to the following final speeds. In each case, find the acceleration (magnitude and algebraic sign) and whether or not the car is decelerating.
(a) The final speed is 28.1 m/s.
m/s2 and the car is ---Select--- accelerating decelerating
(b) The final speed is 21.5 m/s.
m/s2 and the car is ---Select--- accelerating decelerating

Answer 1

use the equations
v(t)=v0+a*t

a)v(5.1)=-28.1=
-27+a*5.1
solve for a
a=-1.1/5.1
accelerating left (negative), which would be decelerating right

b)v(5.1)=-21.5=
-27+a*5.1
solve for a
5.5/5.1=a

decelerating the left motion, which is a right direction acceleration

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