The contact angle for a water droplet on polymethyl-methacrylate (PMMA) is 80°. Assume that the surface tension for PMMA is 0.039 N/m. What is the value of the interfacial tension between water and PMMA at 25°C?
What will be an ideal response?
From Table 3.2 the surface tension of water is 0.072 N/m. Inserting the known values of surface tension into Young’s equation results in:
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Conservation of Momentum: Consider two less-than-desirable options. In the first you are driving 30 mph and crash head-on into an identical car also going 30 mph. In the second option you are driving 30 mph and crash head-on into a stationary brick wall. In neither case does your car bounce back from the thing it hits, and the collision time is the same in both cases. Which of these two situations would result in the greater impact force on your car?
A. hitting the other car B. hitting the brick wall C. The force would be the same in both cases. D. None of these choices are correct.
How does a gas cloud become hot?
What will be an ideal response?
Each rolling wheel of a railroad train is tapered. Compared with the wide part, the narrow part of the wheel has a tangential speed that is
A) less. B) greater. C) the same for both.
Hurricanes are more likely to form near
A) warm waters where the air is humid. B) warm waters where the air is dry. C) cold bodies of water where the air is humid. D) cold bodies of water where the air is dry.