科学知识（scientific knowledge）.docVIP

科学知识（scientific knowledge） Physics knowledge point Chapter 1: walking into the physical world 1 、 a science in the study of the laws and physical structures of various physical phenomena such as light, heat, force, sound, electricity, etc. 2, observation and experiment are important sources of physical knowledge 3, the tool length measurement scale, the basic unit of length is the meter, the symbol is m; common units and km (km) (DM), cm and DM (CM), mm (mm), (m), nano micron (nm) etc.. The conversion relationship between them is... 1km=1, 000m, lm=l0dm, ldm=l0cm, lcm=l0mm 1mm=1 000 mu n l mu m=1 000nm 4. Records of length measurements include accurate values, estimates, and units. 5. Error: the difference between measured and true values is called error. The causes of errors are: (1) relating to the person who is measuring; and relating to the tools of measurement. Any measurement results are error, the error can only be minimized, can not be absolutely avoided; but mistakes can be avoided. The method of reducing errors is: (1) using more precise measuring tools; adopting more reasonable measuring method; The average value was measured several times. 6, the time measurement tools are stopwatch, time international basic unit is seconds, symbol is s; commonly used units are hours (H), points (min) and so on. The conversion relationship between them is 1h=60min lmin=60s 7, the main process of scientific inquiry is to raise questions, conjectures and assumptions, specify plans and design experiments, conduct experiments and collect data, analyze and demonstrate, evaluate, communicate and cooperate with each other The second chapter: sound and environment 1, produce: the sound is produced by the vibration of the object, the vibration stops, the sound stops; the vibration sounds the source of the call 2, spread: the sound transmission needs medium, the vacuum can not transmit sound. Sound travels as a wave in a medium; in different media it travels at a different rate; g