1.

A car travles a distance `A` to `B` at a speed of `40km//h` and returns to `A` at a speed of `30km//h`. (i) What is the average speed of the whole journey? (ii) What is the averege velocity?

Answer» (i) Let `AB = s, `time takemn to go form `A` to `B`,
`t = (s)/(40)h`
and time taken to go form `B` to `A,t_(2) = (s)/(30)h`
`:.` total time taken `=`
`t_(1) +t_(2) = (S)/(40) +(s)/(30) = ((3+4)s)/(120) = (7s)/(120)h`
Total distance travelled `=s +s = 2s`
`:.` "Average speed" `= ("total distance travelled")/("total time taken")`
`= (2s)/(7s//120) = (120xx2)/(7) =34.3km//h`
(ii) Total displacement `=` zero, since the car returns to the original position.
Therefore,
average velocity `= ("total displacement")/("time taken") = (0)/(2t) = 0`


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