1. CHAPTER 13. 평형과 탄성
평형 (Equilibrium)
평형 조건
중력 중심 (Center of Gravity)
정적 평형의 예
불확실한 (Indeterminate) 구조
탄성 (Elasticity)

2. : Static Equilibrium (정적 평형) Section 8-5

3. 13-2 평형 조건 병진운동 : 회전운동 : (balance of force) (balance of torques) 2 차원
13-2 평형 조건
병진운동 :
(balance of force)
회전운동 :
(balance of torques)
2 차원
일정한 속도로 미끄러지는 Hockey puck

4. 13-3 중력 중심 (Center of Gravity)
Center of Mass = Center of Gravity

5. 13-4 정적 평형의 예
Scale readings?

8. Find Tc and F on the hinge.

9. Rock climber resting
Find N, and h.
Best position to rest.

10. 13-5 Indeterminate Structure
For 2-dimensional problems,
2 Fx, Fy
1 z
3 unknowns  solvable
What if we have 4 unkowns?
 indeterminate
Need elasticity to solve them!

11. Spring model of atomic “lattice”
13-6 탄성 (Elasticity)
Spring model of atomic “lattice”
Tensile stress
(인장 변형력)
(b) Shearing stress
(층 밀리기 변형력)
(c) hydraulic stress

12. Stress = modulus x strain
constant of proportionality = modulus of elasticity
Tension and Compression (인장과 압축)
Ultimate Strength의 차이 :
콘크리트 : 압축 (강) 장력 (약)

13. 층 밀리기 :
체적의 변형 :

14. Find Stress, elongation and strain of the rod.
At the bottom of the Pacific Ocean, p = ~ 4107 N/m2 (~ 4000 m 깊이)
B(water) = 2.2109 N/m2 and B(steel) = 161010 N/m2
Find Stress, elongation and strain of the rod.
81 cm
R=9.5 mm
F = 6.2 104 N F