L20EX1-Firetruck Alternate Solutions

# L20EX1-Firetruck Alternate Solutions - To decrease the...

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Problem Type: Find: Given: I o = 14,000 kg-m 2 , m= 200 kg, CG= (3,4) m Force at O and angular acceleration of the ladder First Step? Rigid Body Kinetics FBD and MAD. Asks for forces at O, so will do MAD and FBD for the ladder. Do it. O x O y mg ma Gx ma Gy I G α x y Gx x a m F = α O O I M = Gy y a m F = To decrease the angle of elevation of the stationary 200- kg ladder, the gears that raised it are disengaged, and a fraction of a second later a second set of gears that lower it are engaged. At the instant the gears that raised the ladder are disengaged, what is the ladder’s angular acceleration and what are the components of force exerted on the ladder by its support at O ? The moment of inertia of the ladder about O is I O = 14,000 kg-m 2 , and the coordinates of its center of mass at the instant the gears are disengaged are x = 3 m and y = 4 m. What if the truck is accelerating forward at 3 m/s 2 as the ladder is being lowered?

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