丫蘋果汁丫 發表於 10-11-2010 14:21:20

PHY問題 /口\

al 1998,paper iiA Q3同 2005,paperiiA,Q3

看似好簡單,,點知自己計上手發覺計唔到答案t^t

趕羚羊 發表於 3-1-2011 18:36:02

回復 1# 丫蘋果汁丫
98:
Let the required force br F
P-Q=3ma.......(1)
F-Q=2ma.......(2)
(1)/(2):
2P-2Q=3F-3Q
2P+Q=3F
      F=(2P+Q)/3
04:
Let the required distance be x
by s=ut+1/2at^2
   x=5t^2
For t,



http://img543.imageshack.us/img543/589/61144139.png
      x=Vx (t)
40cosθ=(t)50cosθ
          t=4/5
thus,
   x=5(4/5)^2
       =16/5
       =3.2m
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