after starting from rest, a car acceleraters uniformly 1.2 m/s^2 for 20 s. it then continues driving at a constant velocity for 19s longer. what is the average velocity for 39 s ?
avg velocity=distance/time
distance = 1/2 a t^2 + vf*19
where vf=20*1.2
distance=1/2*1.2*20 + 20*1.2*19
time= 39sec
compute avg velocity, distance/time