Question

A car traveling west in a straight line on a highway decreases its speed from 30.0 meters per second to 23.0 meters per second in 2.00 seconds.The Cars average acceleration during the time interval. is

Answer 1

Acceleration, a =  (v - u) / t

Initial Velocity, u = 30 m/s
Final Velocity, v  =  23 m/s
time                 t  =  2.00 seconds

a = (23 - 30) / 2
a = -7 / 2 = -3.5 m/s2

So the acceleration  is negative, which means it is a deceleration of 3.5 m/s2.