Bathroom scale

For example, kitchen or bathroom scales could be equipped with fingerprint recognition systems, thus giving access only to a limited number of users. Bathroom scales could also have a voice recognition system with a limited vocabulary, and for limited applications. 

There are many examples in our everyday life in which the calibration of a measuring device is important. When we step on the bathroom scale, we want to be assured that the scale reads our correct weight. When we measure the body temperature of our sick child, we want the temperature that is displayed to be correct. When we fill our car s gas tank at the gas pump, we want the pump to display the correct number of gallons and therefore the correct cost. In other words, we want these devices to be properly... 

From the definitions and examples above, it should be clear that metrological traceability is established by a series of comparisons back to a reference value of a quantity. In the mass example it is easy to picture a number of scientists with ever more sophisticated balances comparing one mass with another down the chain of masses from the international prototype of the kilogram to bathroom scales. This is known as a calibration hierarchy. A mass farther up the chain is used to calibrate the next mass down the chain, which in turn can be used to calibrate another mass, and so on, until the final measurement of the mass is made. 

Figure 7.5. Metrological traceability of mass measured by bathroom scales.

Any measurement is only as good as the skill of the person doing the work and the reliability of the equipment being used. You ve probably noticed, for instance, that you get slightly different readings when you weigh yourself on a bathroom scale and on a scale at the doctor s office, so there s always some uncertainty about your real weight. The same is true in chemistry—there is always some uncertainty in the value of a measurement. 

Measurement Bathroom Scale Lab Balance Analytical Balance... 

Despite their general lack of accuracy, their popularity is understandable. Their limited accuracy and reliability are more than sufficient, however, for the demands of grocery stores or bathroom scales. To use anything more complicated or expensive when the need is not justified is a waste of time and money. 

A set of weighings is done with a bathroom scale that registers 2 lb with no load (Figure 2.8). Each weighing results in a reading of 117 lb. 

Figure 2.8 Bathroom Scale If a bathroom scale is not adjusted to read zero when no load is on it, the results it yields with a load may be precise but probably not accurate. For example, if it reads 2 lb with no load, each time a person uses the scale, it will probably read 2 lb heavier than his or her true weight.

If we try to weigh one grain of rice on a bathroom scale, we get an inkling of the very much more difficult task of weighing atoms. (The ratio of the mass of an atom to that of the smallest mass weighable on any balance is about 10 g/10 g, or 10 . This is much lower than the ratio of the mass of a grain of rice to that of a person, which is about 10 g/10 g, or 10 . )... 

It is very important to understand the assumptions that are inherent in a particular model before you use it to interpret observations or to make predictions. Simple methods usually involve very restrictive assumptions and can only be expected to yield qualitative information. Asking for a sophisticated explanation from a simple model is like expecting to get an accurate mass for a diamond by using a bathroom scale. 

We all have our ways of knowing when we re overweight. Our clothes don t fit the way they used to. We loosen our belts a notch. Stepping on the bathroom scales isn t something we really want to... 

Use a bathroom scale to weigh yourself, your science textbook, and a gallon of milk. Divide your measurements by 2.2 to calculate the mass of each object In kilograms. 

Probably the most basic of all measurements in a chemistry laboratory are those of mass and volume. Mass is a measure of the quantity of matter as indicated by its weight, or the effect of the gravitational force on the mass. For example, the mass of our body is measured whenever we step onto a bathroom scale. Volume is a measure of how much space a quantity of matter occupies. In the kitchen, when a recipe calls for two cups of milk, the reference to two cups is a reference to the volume of the milk needed. 

You find an old bathroom scale at a garage sale on your way home from getting... 

Mass and weight Have you ever used a bathroom scale to measure your weight Weight is a measure not only of the amount of matter but also of the effect of Earths gravitational pull on that matter. This force is not exactly the same everywhere on Earth and actually becomes less as you move away from Earths surface at sea level. You might not notice a difference in your weight from one place to another, but subtle differences do exist. 

A digital bathroom scale gives you the following four readings in a row 155.2, 154.8, 154.9, 154.8 lbs. How would you record your weight ... 

You can imagine a similar situation in everyday life. On a bathroom scale, you weigh 158 lb. Take off your wristwatch, and you still weigh 158 lb. Within the precision of the measurement, the weight of the wristwatch is so small compared with your body weight that it can be neglected ... 

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