A girl walks along a straight road from A to B with an average speed 3m s-1.
She then returns from B to A along the same road with an average speed 2m s-2. Find the average speed of the girl for the whole journey.
A.2.24ms-1 B.2.4ms-1 C2.45ms-1 D2.5ms-1
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2008-12-01 1:18 am
回答 (1)
2008-12-01 5:45 am
✔ 最佳答案
有一個女仔以3MS^-1既速率由A點走去B點.之後佢用2MS^-1既速率(我諗你打錯左,唔係-2係-1,因為之前寫住average speed)由B點走番去A點.求她的平均速率.Let s be the distance of the journey.t1 be the first time travel time,t2 be the second time travel time.
v=s/t1 v=s/t2
3=s/t1 2=s/t2
t1=s/3 t2=s/2
average speed=total distance/total time
average speed=2s/(s/3+s/2)
=2.4ms^-1
參考: me
收錄日期: 2021-04-25 23:15:20
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