Question

When the velocity is constant, can the average velocity over any time interval differ from instaneous velocity at any instant? If so, give an example, if not explain why.

Answer 1

If the velocity is constant, the body is moving along a linear path.
We can also say that it is moving with Constant Speed.
Anything that performs motion with constant speed performs uniform motion.
Now we don't need to consider differnt time intervals for calculation of  average spped as the body is travelling with same speed and travels equal distance everytime.

Answer 2

If velocity in magnitude and direction is constant. then,  there is no acceleration. This is true for components of acceleration in the direction of velocity or perpendicular to velocity.

acceleration = time rate of change of instantaneous velocity  = 0

So instantaneous velocity is always same as average velocity.