BME%20551%20Homework%201%20solution - BME551 Homework#1 :...

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1 BME 551 Homework # 1 1/14/09 Heterogeneous Nano Structures:Multiscale structures with NEMS and MEMS components Surface Tension 1. Define surface tension in terms of force and length. Provide the units Surface tension ( σ ) is defined as the ratio of the magnitude of force ( F ) tangentially applied to the surface of a liquid to the length: ( L ) σ =F/L [n/m] or [dyn/cm] 2. Define Mc (The minimal requirement for static stability on the surface). 1 = = P Mg M c σ , where M denotes mass, g force of gravity, σ surface tension, and P the curvature parameter. 3. What parameters are required to keep the paper clip afloat? To remain stationary on water, a M c ratio will be less than 1. 4. What are the chemical bonds underlying the surface tension? (Hint: Google) a. Hydrogen bonds 5. You were commissioned to design a water robot strider by the Defense Department. This water strider would be able to penetrate into the sewage system underneath the former Soviet Union KGB building. What parameters will influence your design? (Hint: the ratio between the
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