HW__11_F05

# HW__11_F05 - at what angle relative to horizontal should...

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Physics 112 Homework #11 Fall 2005 Read: Chapter 11 (intro. + sections 11.1 thru 11.3) For discussion: Chapter 11: Qs: #Q11.7, Q11.10, Q11.14, Q11.15, Q11.18 (not turned in) Due Friday, Nov. 11 at lecture: #11.10 [Leaning Ladder] #11.11 [Diving Board] #11.52 [Truck on Drawbridge] #11.73 [Farmyard Gate] #11.44 [Pickup Truck] HINTS: You should interpret the specified weights that "rest on the front and rear wheels" as the magnitudes of the normal contact forces acting upward on those wheels due to the ground. The first thing to do is locate the truck's CM without the crate. Then you can work the rest of the problem. #11.67 [Carrying a Crate] Please add: (b) At what angle would the crate have to be tipped up from horizontal in order for the person on the left to support the crate's entire weight? #11.72 [Wheel on Curb] Please add: (d) If the force F is applied at the center of the wheel,
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Unformatted text preview: at what angle relative to horizontal should the force be applied so that it can have the smallest magnitude needed to raise the wheel over the curb? Please illustrate your answer with a carefully drawn diagram. 1. [Lifting] A person bends over and lifts a 50 lb object with their back in the horizontal position (a terrible way to lift something!. ..and we'll see why in this problem). The back muscle, attached at a point two-thirds up the spine from the hip pivot, maintains the position of the back, and the angle between the spine and this muscle is 12°. Using the simplified mechanical model in the diagram on the right and taking the weight of the upper body to be 80 lb, find (a) the tension in the back muscle and (b) the compression in the spine. (c) How do these forces compare with the weights of the object and the upper body?...
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