# HW2 - spine a Calculate the total forward-bending moment at...

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University of California, San Diego, Department of Bioengineering BE 109: Statics and dynamics Issued: 01/19/06 (Thursday) Homework Set 2 Due: 01/26/06 (Thursday) Exercise 1. A 200 kg crate is supported by two rope-and-pulley arrangements as shown below. Determine for each arrangement the tension (in Newtons) in the rope and the distance that the rope at point A has to move in order to lift the crate by 30 cm. (Assume that the pulley is frictionless and the rope is very flexible.) Figure 1 Problem 1 . Consider the free body diagram for the elbow joint with a weight and an applied load on the hand as shown in Figure 3. Note the upper arm and forearm are represented as solid straight lines, and the hand is a circle. Assume that there is no moment at the elbow E and that d1=0.038m, d2=0.15m, and d3=0.45m. What is the net muscle force? Figure 2 0.5 N 75 o E upper arm lower arm A A (a) (b)

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Problem 2. The technique employed during lifting influences the loads on the lumbar
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Unformatted text preview: spine. a) Calculate the total forward-bending moment at the vertebra shown exerted by the external forces in each of the 3 following cases in which a person picks up a weight of 300 N (denoted P), which is pulled by a force of 1 N. The weight of the upper torso of the person is 450 N (denoted W). i) L w is 27cm, L p is 42cm; H is 30cm ii) L w is 19cm, L p is 37cm; H is 30cm iii) L w is 26cm, L p is 52cm; H is 30cm. Figure 3 b) Assuming zero moment at the disc, calculate the force produced by the contraction of the erector spinae muscle (M) in the last case, which acts at a lever arm of 0.05m from the lumbar disc and at the same angle as the spine, which is 35 degrees from vertical. c) Calculate for the last case the total reaction force, R, on the disc and the angle at which it acts. (Hint: this reaction force does not act at the same angle as the muscle force, M) 1 N 1 N 1 N H H H...
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HW2 - spine a Calculate the total forward-bending moment at...

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