The ability to distinguish between acceleration and velocity will be critical to your understanding of many other concepts in this course. Some of the most prevalent issues arise in interpreting the sign of both the velocity and acceleration of an object. I would recommend reading through the section "The Sign of the Acceleration" carefully. An object moves with a positive acceleration. Could the object be moving with increasing speed, decreasing speed or constant speed?

Object could only be moving with increasing speed.

Explanation:

Let us consider the general formula of acceleration:

a = (Vf - Vi)/t

Vf = Vi + at   equation 1

where,

Vf = Final Velocity

Vi = Initial Velocity

a = acceleration

t = time

FOR POSITIVE ACCELERATION:

Vf = Vi + at

since, both acceleration and time are positive quantities. Hence, it means that the final velocity of the object shall be greater than the initial velocity of the object.

Vf > Vi

It clearly shows that if an object moves with positive acceleration. It could only be moving with increasing speed.

Solving the same equation for negative acceleration shows that the final velocity will be less than initial velocity and object will be moving with decreasing speed.

And for the constant velocity final and initial velocities are equal and thus, acceleration will be zero.