16.61 Aerospace Dynamics Spring 2003 This analysis extends to rigid body case Rigid body is a collection of masses e Masses held at a fixed distance i Virtual work for the internal constraints of a rigid bod displacement is zero Example: Body sliding on rigid surface without friction Since the surface is rigid and fixed, Or=0, >w=0 For the body, SW=R.Or, but the direction of the virtual displacement that satisfies the constraints is perpendicular to the constraint force. Thus sW=0 Massachusetts Institute of Technology C How, Deyst 2003 (Based on Notes by Blair 2002)16.61 Aerospace Dynamics Spring 2003 This analysis extends to rigid body case • Rigid body is a collection of masses • Masses held at a fixed distance. ! Virtual work for the internal constraints of a rigid body displacement is zero. Example: Body sliding on rigid surface without friction Since the surface is rigid and fixed, 0, 0 s δ r W = → = δ For the body, δW = • R1 δ 1 W r , but the direction of the virtual displacement that satisfies the constraints is perpendicular to the constraint force. Thus δ = 0. Massachusetts Institute of Technology © How, Deyst 2003 (Based on Notes by Blair 2002) 5