Question

when the velocity of body is variable then 1. speed may be constant 2. acceleration may be constant 3. average acceleration may be constant. 4. all of these.

Answer 1

4. all of these
1. when object is moving on circular path.
2. when object is in free fall
3. when object is in Free fall.

Answer 2

Answer: (3) average acceleration may be constant.

Velocity is defined as the displacement of an object per unit time.

As acceleration is the rate of change of velocity per unit time and then it would vary as the velocity of an object varies.  However, the average acceleration can be contsant which is the net acceleration for the whole displacement.