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12.2 å¯å离åéçå¾®åæ¹ç¨ä¸ä¸é¶çº¿æ§å¾®åæ¹ç¨
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2.<br />
dv<br />
m<br />
dt<br />
=<br />
<br />
mg<br />
−<br />
kv<br />
<br />
dv dt<br />
∫ = ∫ <br />
mg − kv m<br />
1<br />
t<br />
− ln( mg − kv)<br />
= + c1 k<br />
m<br />
<br />
<br />
v| t =<br />
= 0 c<br />
= −<br />
∴<br />
v<br />
0<br />
=<br />
mg<br />
k<br />
+ ce<br />
<br />
−<br />
v<br />
k<br />
m<br />
t<br />
=<br />
( c<br />
mg<br />
k<br />
mg<br />
k<br />
e<br />
= −<br />
(1 −<br />
e<br />
-kc1<br />
k<br />
−<br />
k<br />
m<br />
t<br />
)<br />
).