THEORYMECHANICS1902Electronic teaching planChapter3Plane GeneraForce SystemCollege of Mechanical andVehicle Engineering王晓君
THEORY MECHANICS Electronic teaching plan Chapter3 Plane General Force System College of Mechanical and Vehicle Engineering 王晓君
Chapter3 Plane General Force System> 3.1 Simplification of a point in the plane actingon a plane general force system> 3.2 Simplified results for plane general forcesystem> 3.3 Equilibrium conditions and equations of planegeneral force system> 3.4 Plane parallel force system> 3.5 Equilibrium, statically indeterminate andstatically indeterminate problems of object systems> 3.6 Calculation of internal forces of planestatically determinate truss
➢ 3.1 Simplification of a point in the plane acting on a plane general force system ➢ 3.2 Simplified results for plane general force system ➢ 3.3 Equilibrium conditions and equations of plane general force system ➢ 3.4 Plane parallel force system ➢ 3.5 Equilibrium, statically indeterminate and statically indeterminate problems of object systems ➢ 3.6 Calculation of internal forces of plane statically determinate truss Chapter3 Plane General Force System
3.1 Simplification of a point in the plane acting on a planegeneralforcesystemStringersFloorbeamsPlanegeneral force system:Anyforce systemin which the lines ofaction ofallforces are in the same plane and neither converge to a point nor paralleltoeach otheris calledaplanegeneral force system
3.1 Simplification of a point in the plane acting on a plane general force system Plane general force system：Any force system in which the lines of action of all forces are in the same plane and neither converge to a point nor parallel to each other is called a plane general force system
3.1 Simplification of a point in the plane acting on a planegeneral force system一.Translation theorem oflines offorceFF'mB。BBEF=F=AAAoF=F=-FUInstructions:Theoursan pnle translatn an tha same rigidbody parallelly fromit2. pount efartiorpiegsaybspecifiedepaint ioutbrerigid body, but acouple of forces must be attached to the plane determined by theCompositefo.Oanlethonpeaified p fintcewhose sonaerbupltheacforde of forcesis egual to the moment of the force at the specified point4.But a force + a couple
一. Translation theorem of lines of force Theorem: a force acting on a rigid body may move parallelly from its point of action to any specified point in the rigid body, but a couple of forces must be attached to the plane determined by the force and the specified point, whose moment of the couple of forces is equal to the moment of the force at the specified point. A B F B A F F F = A B m F = F F' F'' = = − Instructions: 3.On the contrary，a force a couple+a force Composite 4.But a force ≠ a couple Disassemble 2. One force a force + a couple 1.You can only translate on the same rigid body。 3.1 Simplification of a point in the plane acting on a plane general force system
3.1 Simplification of a point in the plane acting on a planegeneral force system二. Plane general force system simplifies to a point.VytFFmIR'Am2Mo二O0xmnx(b)(c)(a)F'= F(i=1.2..n), m, =mo(F)(i =1.2...n)
O A1 A2 An F1 F2 Fn (a) F F (i 1.2 n) , m m (F )(i 1.2 n) i i i O i = = = = 二. Plane general force system simplifies to a point. O F1 m1 F2 m2 Fn mn x y (b) = O R MO x y (c) = 3.1 Simplification of a point in the plane acting on a plane general force system