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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? |
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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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