CBSE Class 9 Answered

Average speed = ( distance travelled ) / time

Average velocity = ( displacement ) / time

If an object is moving,  then distance travelled will be greater than zero .

Hence average speed is greater than zero.

In the motion of an object displacement can be zero if starting point and ending point are same.

For example moving on a circular track so that starting point and ending point is same.

In this case displacement is zero , while distance travelled equals circumference of circular path.

hence if displacement is zero , then average velocity is zero.