Suppose you increase your walking speed from 4 m/s to 13 m/s in a period of 1 s. What is your acceleration? m/s2

Well the formula for a is a = { vf - vi} : t

where vf is final velocity vi is initial velocity and t is time

thus substituting in the equation you get

a = {13-4} : 1

= 9 m/s2 in the direction of Motion (acceleration is a vector)