# Defining Uniform Motion

According to Wikipedia the definition of motion is:

In physics, motion is a change in position of an object with respect to time. Motion is typically described in terms of displacement, distance, velocity, acceleration, time and speed.

The definition of uniform motion is that the object is supposed to cover equal distances in equal intervals of time. This means that the object in motion will have constant velocity. But when we are talking about uniform motion, why is it defined only in the terms of velocity and not acceleration or displacement?

The definition of uniform motion is that the object is supposed to cover equal distances in equal intervals of time.

Well, it isn't defined from velocity. As you clearly write it here yourself. That is your own interpretation. You could just as well have said that "that means that the acceleration must be constant, so why do they define it from acceleration and not velocity?"

Uniform motion means all those things: Constant velocity, constant acceleration, constant displacements during each time interval etc.

• But when an object is moving with a constant acceleration of 'a' m/s^2 and a is not 0, is it correct to say that the object is in uniform motion? Jun 26, 2016 at 4:52
• Only when all the parameters are constant (velocity, acceleration, displacement for every time interval...). Think of the circular motion as the best example of constant nonzero acceleration and also constant velocity. Jun 26, 2016 at 4:54
• So for an object to be in uniform motion, it's supposed to have all these parameters constant? Jun 26, 2016 at 5:00
• Yes. Like a steady current in an electric circuit. All the considered parameters must be constant. Jun 26, 2016 at 5:04
• Steeven's answer is a little misleading I think: velocity is the differential with displacement with respect to time, so if velocity is constant, displacement per unit time is also constant. Acceleration is the derivative of velocity with respect to time so if velocity is constant then acceleration is zero.
– user107153
Mar 2, 2018 at 12:08

In uniform velocity, changes occur uniformly is the cause of acceleration but in constant velocity no changes occur, then the acceleration is zero.