初中物理知识点总结(精简版).pdf

大丈夫处世，不能立功建业，几与草木同腐乎？——《罗贯中》 初中物理知识点总结 (精简版) Chapter 1: Knowledge of Sound Phenomenon 1.Sound n: It is produced by the n of an object. 2.Sound n: Sound is transmitted through a medium 。Vacuum cannot transmit sound 。Usually 。the sound we hear is transmitted through the air. 3.Speed of sound: The speed of sound in air is 340 meters/second 。Sound travels XXX 。and XXX. 4.Three characteristics of musical notes: Pitch 。loudness 。 XXX(1) XXX of a sound and is related to the frequency (ƒ) of the vibrating body 。(2) Loudness refers to the volume of a sound and is related to the amplitude of the vibrating body 。the source of the sound 。and the distance een the source and the listener 。(The unit of loudness is decibel (dB) 。and normal speech is around 60 dB.) 5.Ways to ce noise: (1) ce it at the source 。(2) ce it during n 。 (3) ce it at the ear. 以家为家，以乡为乡，以国为国，以天下为天下。——《管子·牧民》 谋事在人，成事在天！——《增广贤文》 6.Audible sound: Sound waves with frequencies een 20 Hz and 20,000 Hz 。Ultrasonic waves have frequencies higher than 20,000 Hz 。XXX 20 Hz. 7.Characteristics of ultrasonic waves: They have good nality 。 strong rating power 。XXX sonar 。B-mode ultrasound 。XXX 。 ultrasonic cleaning machine 。and XXX. Chapter 2: Knowledge of States of Matter 1.XXX: It XXX of an object。The instrument used to measure it is a thermometer 。which is based on the XXX liquids. 2.Celsius temperature (℃): The unit is Celsius degree 。The n of 1 Celsius degree is that the temperature of a mixture of ice and water is defined as 0 degrees 。and the temperature of boiling water under standard atmospheric pressure is defined as 100 degrees 。The range een 0 and 100 degrees is divided into