1(a) The average velocity during any time interval is the displacement during that interval dividedby the duration of the interval:vavg=∆x/∆t, where∆xis the displacement and∆tis the timeinterval. In this case the interval is divided into two parts. During the first part the displacementis∆x1= 40 km and the time interval is∆t1=(40 km)(30 km/h)=1.33 h.During the second part the displacement is∆x2= 40 km and the time interval is∆t2=(40 km)(60 km/h)=0.67 h.Both displacements are in the same direction, so the total displacement is∆x=∆x1+∆x2=40 km + 40 km = 80 km. The total time interval is∆t=∆t1+∆t2.33 h + 0.67 h = 2.00 h.The average velocity isvavg=(80 km)(2.0h)=40km/h.(b) The average speed is the total distance traveled divided by the time. In this case the total
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