Physics – Scientific Method – Measurements. Chapter zero Physics – Scientific Method – Measurements.

What is physics? Physics is the study of the physical world, from motion and energy to light and electricity.

The Scientific Method

Make observations and collect data that lead to a question. Formulate and objectively test hypotheses by experiments. Interpret results, and revise the hypothesis if necessary. State conclusions in a form that can be evaluated by others.

Measurements & Units When scientists make measurements, they report their results as numbers and units. Units are standard measurements or standard quantities used to compare, like foot, cup....

The platinum-iridium cylinder shown here is the primary kilogram standard for the United States.

As a physical quantity is measured, the number describing it, depends on the unit used (e.g. the classroom height equals 3 meters or 300 centimeters). Three basic things can be measured: mass, length (or distance), and time.

SI is the standard measurement system for science When scientists do research, they must communicate the results of their experiments with each other and agree on a system of units for their measurements. In 1960, an international committee agreed on a system of standards. This system of units is called the Système International d’Unités (SI).

Physical quantity SI unit Abbreviation of unit Mass kilograms kg Distance or length meters m Time seconds s

SI uses prefixes to accommodate extremes Physics is a science that describes a broad range of topics and requires a wide range of measurements, from very large to very small. For example, distance measurements can range from the distances between stars (about 100 000 000 000 000 000 m) to the distances between atoms in a solid (0.000 000 001 m). Because these numbers can be extremely difficult to read and write, an approach commonly used in SI is to combine the units with prefixes that symbolize certain powers of 10. Example:

The mass of this insect can be expressed several different ways: 0 The mass of this insect can be expressed several different ways: 0.00001 kg, 0.01 g, or 10 mg.

Precision, accuracy, & significant figures. No measurement is perfect; every measurement is done with some error. And this error must be minimized. This error may be due to: Lack of calibration. The way the measurement is done. The scale error:

Lack of calibration For example, a digital balance must read zero when empty. Also the balance has to read 1 Kg when a standard one kilogram-mass is put on. A stopwatch must be reset ( read zero) at the beginning of time counting; else the initial non-zero reading must be taken in consideration

Precision, accuracy, & significant figures. No measurement is perfect; every measurement is done with some error. And this error must be minimized. This error is due to: Lack of calibration. The way the measurement is done. The scale error:

Precision, accuracy, & significant figures. No measurement is perfect; every measurement is done with some error. And this error must be minimized. This error is due to: Lack of calibration. The way the measurement is done. The scale error: The precision of any measurement is limited by the instrument used to measure it. This inherent limitation is called the scale error or scale uncertainty of the instrument. To get more precision, you need a more precise (more expensive and usually more difficult to use) instrument.

The scale error In many situations, you can improve the precision of a measurement. This can be done by making a reasonable estimation of where the mark on the instrument would have been.

Significant figures help keep track of imprecision It is important to record the precision of your measurements so that other people can understand and interpret your results. A common convention used in science to indicate precision is known as significant figures. In the case of the measurement of the pencil as about 18.2 cm, the measurement has three significant figures. The significant figures of a measurement include all the digits that are actually measured (18 cm), plus one estimated digit. Note that the number of significant figures is determined by the precision of the markings on the measuring scale.

Scientific Notation To learn about: 1) scientific notation definition, and 2) writing numbers in scientific notation 3) have an assessment about scientific notation Please go through: http://www.nyu.edu/pages/mathmol/textbook/scinot.html

For doing the assessment go through: www.edinformatics.com/math_science/scinot6.htm