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Unformatted text preview: 1 W eek 10 © P Commins 1 Week 10 Mech226 Virtual Work Chapter 10.15 and 11.10 Norton W eek 10 © P Commins 2 Energy methods • Newtonian methods provide complete information about forces complex! • Energy methods have easier solutions but provide less information. • Useful if only input and output is required, or simply for a quick check. W eek 10 © P Commins 3 Motivation • What is the driving torque required to keep the mechanism static or in dynamic equilibrium? W eek 10 © P Commins 4 Conservation of Energy • Energy cannot be created or destroyed. • Energy can be converted from one form to another – Potential to Kinetic etc • Most energy can be captured, some is lost in heat • Energy provides the means to undertake work 2 W eek 10 © P Commins 5 Work work = force • distance (distance travelled by the point of application of the force, in the direction of the force) Dot product of two vectors gives a scalar. W = F R i ( ) cos W F D θ = i 90 90 90 θ θ θ < ° = ° > ° Force is doing positive work Force is doing no work Force is doing negative work W eek 10 © P Commins 6 Torque or Work? • Both have units of Nm ( ) vector = × = T F R k R F R F scalar W = = F R i • Work/energy has units of Joules W eek 10 © P Commins 7 Work F and D are vectors, this is a “dot” product i • i = 1, i • j = 0. Therefore, only multiply the same components together…...
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This note was uploaded on 10/27/2009 for the course MECH 226 taught by Professor Weihuali during the Three '09 term at University of Wollongong, Australia.
- Three '09