Couple(p.50) 点 O 回りのモーメント · The moment of the resultant force about any...
Transcript of Couple(p.50) 点 O 回りのモーメント · The moment of the resultant force about any...
工業力学 I(第 2 回)
本日の予定
Statics II(1) Couple (2) Force - Couple System (3) Resultant
Couple(p.50)the moment produced by two equal, opposite, and noncollinear forces
点 O 回りのモーメント
M = a + d( ) × F + a × −F( ) = Fd
a に依存せず
Fig. 2.10
点 O は任意!
Couple(p.50)the moment produced by two equal, opposite, and noncollinear forces
点 O 回りのモーメント
M = a + d( ) × F + a × −F( ) = Fd
a に依存せず
M = rA × F + rB × −F( )= rA − rB( ) × F = r × F rA, rB に依存せず
Fig. 2.10
Couple M is a free vector
点 O は任意!
Couple(p.50)the moment produced by two equal, opposite, and noncollinear forces
点 O 回りのモーメント
M = a + d( ) × F + a × −F( ) = Fd
a に依存せず
M = rA × F + rB × −F( )= rA − rB( ) × F = r × F rA, rB に依存せず
Fig. 2.10
Couple M is a free vector
点 O は任意!
Equivalent Couples
Fig. 2.11(p.51)
✴平行であれば作用線の方向は関係ない. (力の作用点も無関係)
✴作用線間隔と力の大きさが反比例
Force ‒ Couple System力の作用線を平行移動させるとモーメントを加える必要がある
力と偶力は一つの力に置き換えられる
Fig. 2.12(p.51)
ただし,2D だけ!
Problem 2.78(p.57)The force F acts along line MA, where M is the midpoint of the radius alongtheu x-axis. Determine the equivalent force-couple system at O if θ = 40°.
Resultant(2D)
R=F1+F2+F3+!= F∑
Fig. 2.13(p.58)
2D では concurrent (or couple)
危険!
Resultant(2D)
R=F1+F2+F3+!= F∑
Fig. 2.13(p.58)
2D では concurrent (or couple)
危険!
R= Fi∑MO = Mi∑ = Fi di( )∑d =
MO
R
MO は個々の力によるモーメントの和
MO は合力によるモーメント
Fig. 2.14(p.59)
Principle of Moment(p.59)
The moment of the resultant force about any point O equals the sum of the moments of the original forces of the system about the same point.
Fig. 2.15
合力は 0 だが couple となる場合
an extension of Varignon’s theorem to the case of non-concurrent force systems
Problem 2.99(p.65)As part of a design test, the camshaft-drive sprocket is fixed and then the two forces shown are applied to a length of belt wrapped around the sprocket. Find the resultant of this system of two forces and determine where its line of action intersects both the x- and y-axes.
Resultant(3D)
Fig. 2.28(p.89)
R と直交しないモーメント M は 0 にはできない
R=F1+F2+F3+!= Fi∑M=M1+M2+M3+!= ri×Fi( )∑
r1 r2
r3
ri は移動先から元へ
Eq. 2.20(p.89)
Wrench
Fig. 2.30(p.91)M2 を消去できるように R の作用線を平行移動
Fig. 2.29(p.90)
次回の予定
Review I(1) Newton’s Law,Force, Moment / Torque (Vector Operations)
(2) Couple, Force - Couple System, Resultant