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Chapter 2 x̻ࠦɢӻ

精選範例 1 同步練習 1

νɨྡהͪ ∆ABC މ৷ 6m ͍ٙ ∆dG މ νɨྡהͪd༊Ӌ 50N ٙɢ࿁ AeB ɚᓃ

Չࠠːd༊Ӌ 100N ٙɢ࿁ AeBeG ɧ ٙɢॉ΢މОk
ᓃٙɢॉ΢މ߰ʍk€ൗj∆ ٙࠠː൷ֵ 50N

1 2 3m 2m
ᗙ hd൷௟ᓃ h B
3 3 2m
A A 3m

6m 100N
G

B C

2 ഈ
༆ M A = –100 × ( × 6) = –400€N-md 
3
1
M B = 100 × ( × 6) = 200€N-md 
3
M G = 100 × 0 = 0

類題

1. ν̛ྡהͪd100N ʘɢ࿁ A ᓃٙɢॉ M = i B 2m
A
࿁ B ᓃٙɢॉ M = N-mf
B
3m
100N
A 4m

精選範例 2 同步練習 2

νɨྡהͪd༊Ӌ 10N ʘɢ࿁ A ᓃٙɢॉk νɨྡהͪd༊Ӌ 10N ʘɢ࿁ A ᓃٙɢॉk

A A
30° 30°
10N
2m 2m
10N
B B
༆ ν̛ྡהͪd΋Ӌٜ̈ۧ൷ᕎ d ഈ
d = 2 × cos30° 10N
A d
= 3 €m 30°
ð M A = –10 × 3 2m
B
= −10 3 €N-md 
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BD111_CH02.indd 29 23/7/2021 14:57:08