BME 314 Fall 2010 Quiz Answer Key Created by TAs: Eileen Dawson and Prinda Wanakule Quiz 4: October 12, 2010 1. State the two mathematical (or physical) conditions that must hold true when a body is in static equilibrium. (2) In any direction, the sum of all forces must equal zero. +1 point In any direction, the sum of all moments must equal zero. +1 point 2. In the examples discussed in class, which direction do the cells align when subjected to a uniaxial stretch, along the direction of stretch or perpendicular to it? (1) What component (molecule) inside the cell is responsible for this alignment? (1) Perpendicular +1 point Actin (cytoskeleton is ok) +1 point 3. For the following free body diagram write the moment equation at equilibrium with respect to point X. (2) Define a rotational positive/negative convention, ex: clockwise is positive; counterclockwise is positive +0.25 points Depending on their convention, they could have either: F1*d1 - F2*D2 - F3*D3 = 0 (or = sum of moments)
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