Bathtub example

Obviously, clogged drains are not much fun. But free-flowing ones can be. They afford fantastic opportunities for scientific conjecture and experimentation. For example, does water really spiral down the drain counterclockwise in the Northern Hemisphere and clockwise in the Southern Certainly, hurricanes and tornadoes spin in opposite directions above and below the equator. This is due to the so-called Coriolus effect, which is based on the fact that the earth spins in an easterly direction at a speed of about a thousand miles per hour at the equator. As we move north or south the speed decreases, since less distance has to be covered in the same time. Now, imagine that there Is a gigantic bathtub extending from the equator to the North Pole. The water near the equator will travel east much faster than the water near the North Pole. If we pull the plug, the water will spin down the drain counterclockwise due to the... 

Such flashes, inspirations if you like, do not happen while one is thinking in one s study or talking with a student. They turn up like a photograph in the mind at some odd time later (Leo Szilard, for example, got some of his best ideas while soaking in the bathtub). But they don t turn up at all unless one has thought a great deal about the matter. 

If you collect rainwater in a relatively unpolluted area, you will discover that the rainwater is essentially a nonconductor of electricity. A small concentration of carbonic acid from the carbon dioxide in the air added to the rainwater causes the rain water to be a weak conductor. Pure rainwater conducts almost as poorly as distilled water. However, most of the water we use comes from wells, lakes, or rivers. This water has been in contact with soil and rocks, which contain ionic compounds that dissolve in the water. Consequently, tap water conducts electricity. The conduction is not high, but the water can conduct enough current to stop a person s heart. So, for example, a person should not use an electrical appliance when in the bathtub or shower. 

Liquids can also be good conductors of electricity. This is why it is a bad idea to use an electric device near water. For example, never use a hair dryer near a bathtub filled with water. 

Rumelhart et al. offer a much narrower view of a schema than the one taken here. Indeed, what they call a schema hardly differs from a concept. For example, they developed a room model to illustrate schemas in a PDP representation. The model learns to recognize five rooms based on forty descriptors such as toaster, bathtub, television, and so on. The model learns to associate particular features with particular rooms, and in fact it develops concepts for the five rooms. Nevertheless, the knowledge structure built by the model lacks many of the critical features of a schema as outlined in chapters 2 and 3. 

The reason for the use of methyl or ethyl nitrite in this reaction is two-fold. First of all, the matching alcohols are very easily picked up at the hardware or liquor stores. The second reason is that the methyl and ethyl nitrites give a little higher yields at lower temperatures. For example, methyl nitrite gives 90% yield of phenylacetone at a reaction temperature of room temperature. Butyl nitrite, on the other hand, gives a 87% yield at a temperature of SSoC. The possibility of running a batch at room temperature makes bathtub size production easy to envision. 

Oxalic acid (C2H2O4) is a poisonous substance used chiefly as a bleaching and cleansing agent (for example, to remove bathtub rings). Calculate the concentrations of all the species present at equilibrium in a 0.10 M solution. 

Lime soaps Calcium matter which forms as a curd when soap is used in hard water. An example is a bathtub ring. 

The water level h in the bathtub is a more complex example of a state variable, h not only depends upon the water volume F but upon the volume displaced by the person standing, sitting, or lying in it, = h(V, Fj). If the tub had straight walls, i.e., if the cross section A were constant, we could easily write ... 

Fig. 1.9 Volume of water V and water level kina bathtub as examples of state variables.

This is not different from what we learned in the example of the bathtub (compare Sect. 1.6). The way water flows in and out of the bathtub over various paths is also valid here for energy. The energy content W of the area is a state variable, but the amounts of energy W v, W , W , . .. that are exchanged with the... 

Water containing a relatively high concentration of Ca, Mg, and other divalent cations is called hmd water. Although the presence of these ions is generally not a health threat, they can make water unsuitable for some household and industrial uses. For example, these ions react with soap to form an insoluble soap scum, the stuff of bathtub rings. 

Statistical values can also be used to determine expected periods of optimum performance in the life cycle of products, systems, hardware, or equipment. For example, if the life cycle of humans were plotted on a curve, the period of their lives that may be considered most useful, in terms of productivity and success, could be represented as shown in Figure 5.4. This plotted curve is often referred to as the bathtub curve because of its obvious shape. A similar curve can be used to determine the most productive period of a product s life cycle according to the five known phases of that life cycle, as discussed in Chapter 3. The resultant curve, known as a product s reliability curvey would resemble the curve that appears in Figure 5.5. During the breakin period, failures in the system may occur more frequently, but decreasingly less frequently as the curve begins to level toward the useful life period. Then, as the system reaches the end of its useful life and approaches wearout, more frequent failure experience is likely until disposal. 

Another consideration of formulators is that consumers, as stated above, do not view products as being as neatly compartmentalized as manufactmers do. When a consumer wishes to clean a dirty bathtub, for example, they may have tried a cleanser, a dilutable APC, and a specialty spray soap scum ranover to do the job. All of these products are competing for the same job—cleaning soap scum from the bathtub surface. The consumer may use any or all of them to get the job done, according to their own personal standard of cleanliness, desire to apply elbow grease, and evaluation of the surface condition (new or worn, sensitive or impervious, etc.). 

---