1. Visualization of Internal Force 2. Selection of Cut Section 3. Obtaining Internal Force

1. Virtual Cut & Internal Force
1. Visualization of Internal Force
Goal
2. Selection of Cut Section
3. Obtaining Internal Force

2. F F
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Visualization of Internal Force

3. Cross-section of Virtual Cut
F F
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Visualization of Internal Force

4. F F
F F
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Cross-section of Virtual Cut
Visualization of Internal Force

5. F F
F N FN
A pair of forces which have same
intensity and opposite directions
Internal Force
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Cross-section of Virtual Cut
Visualization of Internal Force

6. Selection of Cut Section
within a section without internal force change
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7. Selection of Cut Section
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within a section without internal force change
Within a section between two external forces
＝

8. Selection of Cut Section
F1 F3
F2
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within a section without internal force change
Within a section between two external forces
＝

9. F1 F3
F2
① ②
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Selection of Cut Section
within a section without internal force change
Within a section between two external forces
＝

10. F1 F3
F2
① ②
Virtual cut Virtual Cut
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Selection of Cut Section
within a section without internal force change
Within a section between two external forces
＝

11. Obtaining Internal Force
F1 F3
F2
① ②
Considering equation of equilibrium every section
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12. F1 F3
F2
① ②
F1 N1 N1
F3
＋ ＝ 0F1 N1
−∴ N1＝ F1
F2
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Obtaining Internal Force
Considering equation of equilibrium every section

13. F1 F3
F2
① ②
F1 N1 N1
F3
＋ ＝ 0F1 N1
−∴ N1＝ F1
F2
F1 F2
F3N2 N2
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N2− ＋F3 ＝ 0
∴ N2＝F3
Obtaining Internal Force
Considering equation of equilibrium every section

14. F1 F3
F2
① ②
F1 N1 N1
F3
＋ ＝ 0F1 N1
−∴ N1＝ F1
F2
F1 F2
F3N2 N2
N2− ＋F3 ＝ 0
∴ N2＝F3
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Obtaining Internal Force
Considering equation of equilibrium every section