# Answer to Question #20923 in Mechanics | Relativity for Brad

Question #20923

A car travels at 40 km/h for 50 minutes, then at 90 km/h for 6.0 km. what is the average velocity?

Expert's answer

V1=40 km/h & T1=50 minutes=5/6 hours

V2=90 km/h & S2=6 km

V_av=S_total/T_total

S_total - total distance

T_total - total time

S1=T1*V1 - the distance covered in the first section

S_total=S1+S2=T1*V1+S2

T2=S2/T2 - the time spent on the second section

T_total=T1+S2/T2

V_av=(T1*V1+S2)/(T1+S2/T2)=(40*5/6+6)/(5/6+6/90)=1180/27=43.70 km/h

V2=90 km/h & S2=6 km

V_av=S_total/T_total

S_total - total distance

T_total - total time

S1=T1*V1 - the distance covered in the first section

S_total=S1+S2=T1*V1+S2

T2=S2/T2 - the time spent on the second section

T_total=T1+S2/T2

V_av=(T1*V1+S2)/(T1+S2/T2)=(40*5/6+6)/(5/6+6/90)=1180/27=43.70 km/h

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