[S]Mangoray 發表於 6-10-2008 21:16:36

力學題.花你幾十秒

答案是B,而不是C
為什麼?
http://i350.photobucket.com/albums/q437/mangorayyau/111.jpg

Zend 發表於 6-10-2008 21:18:55

speed = total distance/ time

total distance =2x

time = x/4 +x/6

speed = 2x /(x/4+x/6) = 2x / [(6x+4x)/24] = 48x/10x =4.8 ms^-1

cla981085 發表於 13-9-2009 10:38:00

let total distance = 2d
total time taken = d/4 + d/6

average speed = 2d/(d/4 + d/6)
                     = 4.8ms^-1

kkuukkoo 發表於 24-10-2009 21:39:49

let total distance = 2d
total time taken = d/4 + d/6

average speed = 2d/(d/4 + d/6)
                     = 4.8ms^-1
cla981085 發表於 13-9-2009 10:38 http://www.nakuz.com/bbs/images/common/back.gif
為了方便
個d可以任let@@
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