1. it changes its velocity though out its circular motion because of its constant change in direction and also in its last 20 second due to a decrease in speed
2. 800kmhr^-1
v = s / t
= 2000/2.5
=800kmhr^-1
3. 1000kmhr^-1
v= s/t
= 2000/2
=1000kmhr^-1