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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 = i 90 90 90 < = > 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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- Three '09