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A girl travels along a straight road due east for the first half distance with speed v_(1)and the second half distance with speedv_(2). What is the average speed of the girl ? |
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Answer» Solution :Given : Total distance = s Let the velocity of the girl for the first HALF distance be `v_(1)` Let the velocity of the girl for the second half distance be ` v_(2)` Formula : Time taken`= ("Distance")/("Velocity")` Time takenforthe first half distance `=((s)/(2))/(V_(1)) = (S)/(2v_(1))` Time taken for the second half distance `= ((s)/(2))/(v_(2))= (S)/(2v_(1))` `{:("Total time"),("taken"):}}= (S)/(2v_(1)) +(S)/(2v_(2))` Average SPEED , `v_(av)= (S)/((s)/(2v_(1))+(s)/(2v_(2)))=(2v_(1)v_(2))/(v_(1)+v_(2))` |
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