L20EX1-BarPullingCrate - treated as a particle 2 more...

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The masses of the slender bar and the crate are 9 kg and 36 kg respectively. The crate rests on a smooth horizontal surface. If the system is stationary at the instant shown and a counterclockwise moment of 300 N-m is applied to the bar as shown, what is the resulting acceleration of the crate. Find expressions for a G using relative acceleration Problem Type: Find: Given: Rigid Body Kinetics – Want accel given forces m bar = 9 kg, m crate = 36 kg, M A = 300 N-m a crate First Step? A B Next Step is to apply Newton’s laws. For which piece? x y C EX20.1 – Bar Pulling a Crate FBD, MAD!! Of what? I A α G G ma Gx ma Gy mg T A y A x Ma Cx T Mg N Need I A Both! Newton’s Laws for the rod 5 Unknowns! Newton’s Laws for the crate
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Unformatted text preview: treated as a particle. 2 more Unknowns! 45º θ Now we need to find α! Can do this by using relative acceleration equations Now we have 11 equations and 11 unknowns. A x , A y , T, N, a cx , a Gx , a Gy , α, α BC , a By and a Bx We can then solve for all unknowns. Reflection: Note that the initial acceleration is to the left. This makes sense given that the system is starting from rest and the moment on the bar is Clockwise. It is hard to decided whether the magnitude is correct, instead we have to trust our math. Note that doing the kinetics for plane motion is a long process....
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This note was uploaded on 12/10/2009 for the course ME 212 taught by Professor Staff during the Spring '05 term at Cal Poly.

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L20EX1-BarPullingCrate - treated as a particle 2 more...

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