Answer
a) -0.40 m/$s^{2}$ , car is not decelerating
b) +0.80 m/$s^{2}$ , car is decelerating
Work Step by Step
$a = \frac{v-u}{t}$
The direction in which the car is travelling (left) has been designated as the negative direction.
When an object's velocity and acceleration are in opposite directions, it is decelerating. In both of the given scenarios, the car's velocity is negative
a)
$a = \frac{-29.0-(-27.0)}{5.0} =-0.40$ m/$s^{2}$
Acceleration and velocity in the same direction hence car is NOT decelerating
b)
$a = \frac{-23.0-(-27.0)}{5.0} = +0.80$ m/$s^{2}$
Acceleration and velocity in opposite directions hence car is decelerating
