Question

a car moving at a speed of 25 m/s in the postive direction decelerates to a stop in 5.0 s. The average acceleration of the car over the 5.0s is

Answer 1

V_i = 25 m/s

V_f = 0 m/s

t = 5.0 s

Average acceleration:

$a = \frac{V_f - V_i}{t}$

$a = \frac{0 - 25}{5} = \frac{-25}{5} = - 5 \;m/s^2$ (negative sign indicates deceleration)