1.2PrinciplesofstaticsTwo-force member:A rigid body balanced by only twoforces.It'snotatwo-forcemember
A rigid body balanced by only two forces. Two-force member： It's not a twoforce member 1.2 Principles of statics
1.2Principles of staticsAxiom 3 The principle of addition and subtraction of equilibriumforce system.The rigid body will remain unchanged if a equilibrium forcesystem is added or subtracted from the original force systemactingontherigid bodyInstruction:1. The axiom is the theoretical basis of force systemsimplification.2. For rigid bodies (counter example).3.The force system is not necessarily the equilibriumforce system
Axiom 3 The principle of addition and subtraction of equilibrium force system. The rigid body will remain unchanged if a equilibrium force system is added or subtracted from the original force system acting on the rigid body. Instruction： 1. The axiom is the theoretical basis of force system simplification. 2. For rigid bodies (counter example). 3. The force system is not necessarily the equilibrium force system. 1.2 Principles of statics
1.2PrinciplesofstaticsDeduction 1 : The principle of transmissibilityA force may move along its line of action on a rigid body withoutchanging its action on it.BAF
F A B A force may move along its line of action on a rigid body without changing its action on it. Deduction 1 ：The principle of transmissibility 1.2 Principles of statics
1.2PrinciplesofstaticsDeduction 1 : The principle of transmissibilityA force may move along its line of action on a rigid body withoutchanging its action on it.B三AFF'FF=F'=F
F F = F = F A F F F = B Deduction 1 ：The principle of transmissibility A force may move along its line of action on a rigid body without changing its action on it. 1.2 Principles of statics