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Physics: definitions General

Physics takes care of everything in the various phenomena can be quantitatively determined .

Experimental method:

1. observation of
2. choice of physical
3. forumlazione hypothesis
4. controlled experiment for testing the hypothesis of the experimental law
5. formulazionel
6. formulation of a theory

A theory is a set of principles that allow interpret data and provide phenomena.

Sizes Individuals must be found through the instruments used to measure and we must therefore give an operational definition :
description of the equipment to be used and the procedure for the measurement of the same .

time (seconds, s) should refer to periodic phenomena.
Initially 86 000-th part of a mean solar day, then the period during which take place 9 billion oscillations in a cesium clock .

Length (meters, m): ten-millionth of the distance between the North Pole and the Equator along the meridian passing through Paris, then the distance traveled by light in vacuum in a 300,000,000 th of a second (because the speed of light is constant).

mass (kilogram, kg) equal to the mass of the sample platinum-iridium kept at the Museum of Weights and Measures at Sevres.



Order of magnitude: the power of 10 that best approximates the number to be expressed.

Direct measurement : direct comparison with the size of a 'unit sample.
Indirect measurement: the value obtained using an analytical report between different sizes.

Calibration : an instrument is calibrated when there correspondence between his response and the value of the quantity to be measured.

Characteristics of:

1. Sensitivity: minimum change of considerable magnitude
2. flow or scale: maximum value of the measurement accuracy
3. : little or no difference in repeated measurement
4. Readiness: responsiveness to changes in the size

measurement error

1. error sensitivity depends on the sensitivity of the instrument used. You choose half of the values \u200b\u200bof sensitivity (eg 0.5 cm) and marks: L = (y + / - 0.5) cm
2. random error: multiple causes undetectable
3. Systematic errors (always downwards or upwards): data problems in the instrument and easy to find. A classic error is the systematic ' parallax error, which depends on the position taken by the observer against the instrument.

For a successful experiment, the measurements should be checked several times and then find a measure which approximates the reality better, eliminating as much as possible of the various errors.
The first method is the arithmetic mean between the various measurements, also calculating the maximum error as semidispersione .
Semidispersione : 1 / 2 (maximum extent - at least so far)
At this point, the size will be obtained the mean + / - the semidispersione.