Complete of following sentences

a. The acceleration of the body that moves with a uniform velocity will be ________

b. A train travels from A to station B with a velocity of 100 km/h and returns from station B to station A with a velocity of 80km/h. Its average velocity during the whole journey in ______________ and its average speed is ____________

(a) Zero

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force(acceleration).

(b) Zero, 89 km/h

let the distance from Station A to B be ‘s’ km,

Then the time taken to travel from A to B ‘t1’ = s/100 hours

The time taken to travel from B to A ‘t2’ = s/80 hours.

Total time taken t1+t2

Total Distance Travelled = 2s km

Average speed = = = 89 km/h

Displacement will be zero, because initial and final positions are same.

Average Velocity = = 0