Average velocity =sΔt=vavg
S=∫50vdt=∫50(4t−t2)dt=253m
vavg=25/3m5sec=53msec
Average speed =distance coveredtime taken=distanceΔt
Distance =∫40vdt+∫54(−v)dt=323+73=393m=13m
Average speed =13m5sec
Average acceleration (aavg)=vf−viΔt
vf=4×5−52=20−25=−5
vi=0
aavg=−5−05=−1m/s2