新手任务不要下载（Novice tasks do not download）.docVIP

新手任务不要下载（Novice tasks do not download） Unit formula of physical quantity Name, symbol, name, symbol The quality is m kg kg m=pv The temperature is t degrees Celsius, C degrees Celsius Speed v m / sec, m/s v=s/t Density p kg / M 3 kg/m3 p=m/v Force (gravity) F Newton (cow) N G=mg The pressure is P Pascal (PA) Pa P=F/S Work W Joule (focus) J W=Fs Power P watt (W) w P=W/t Current I ampere (an) A I=U/R Voltage U volts (volts) V U=IR Resistance R ohm (OU) R=U/I Electrical work W Joule (focus) J W=UIt Electrical power P watts (Watts) w P=W/t=UI Heat Q Joule (coke) J Q=cm (T-T degrees) Specific heat C Jiao / (kg degree C) J/ (kg degrees C) In the vacuum, the speed of light is 3 * 108 meters per second G 9.8 Newton / kg 15 degrees C air speed of 340 meters per second Safety voltage not higher than 36 volts Essentials of elementary physics in junior high school I. measurement The length of L: main units: meters; measurement scale; measurement tools: when estimating the minimum scale read next; light unit is a unit of length. The time in seconds; t: the main measurement tools: watch with stopwatch in the laboratory. 1 = 3600 seconds, one second = 1000 milliseconds. 3 M: substances contained in the number of objects called quality. Main unit: kg; measuring tools: scales; laboratory trays; balances. Two. Mechanical movement The mechanical movement: the object position changes of movement. Reference: to judge the motion of an object, another object must be chosen as the standard. This object is chosen as a standard. It is called a reference. The uniform linear motion: Compare the two methods of moving speed: a compares the distance traveled in equal time. B compares the time required to travel by equal distance. Formula: 1 meters per second = 3.6 km / h. Three, force The F force: force is the object role of objects. The forces acting between bodies are always reciprocal. A unit of force: Newton (N). An instrument for measuring force: a dynamometer; a laboratory uses a spring bal