What is power

Power refers to the speed of work done by an object in a unit of time, that is, the power is a physical quantity that describes how fast the work is done. The amount of work is constant, and the shorter the time, the greater the power value. The formula for finding power is power = work / time.

Physical meaning

Physical meaning: A physical quantity that indicates how fast an object performs.

Physical definition: The power done in unit time is called power. Power is the physical quantity that indicates how fast the object is doing work.

formula

Power can be divided into electric power, power of force, and the like. Therefore, the calculation formula is also different.

Electric power calculation formula: P = W / t = UI; in the pure resistance circuit, according to Ohm's law U = IR substituted P = UI can also get: P = I * IR = (U * U) / R

In dynamics: power calculation formula: 1. P = W / t (average power) 2. P = FV; P = Fvcosa (instantaneous power)

Because W=F(f force)×S(s displacement) (the definition of work), the formula for power can also be derived P=F·v:P=W /t=F*S/t=F* V (this formula is suitable for objects to make uniform linear motion)

unit

P represents power, the unit is "Watt", abbreviated as "Watt", and the symbol is "W". W stands for work, the unit is "Joule", referred to as "Joke", and the symbol is "J". "t" indicates time, the unit is "second", and the symbol is "s".

The higher the power, the higher the speed, the higher the maximum speed of the car, and the maximum power is often used to describe the dynamic performance of the car. The maximum power is generally expressed in horsepower (PS) or kilowatts (kW), and 1 horsepower is equal to 0.735 kilowatts. 1W=1J/s

Various titles

Power is the physical quantity that indicates the speed at which an object does work. In physics, the power P = work W / time t, the unit is watt w, the power units we often see in the media are kw, ps, hp, bhp, whpmw, etc., and Italy. Previously used cv, here kilowatt kW is the international standard unit, 1kW = 1000W, with 1000 seconds of work done in 1 second, its power is 1kw. In daily life, we often refer to power as horsepower, and the unit is horse, just like torque is called torque.

On the car, the biggest work machine is the engine. The power of the engine is calculated from the torque, and the formula is quite simple: power (w) = 2π × torque (Nm) × speed (rpm) / 60, after simplifying the calculation Become: Power (W) = Torque (Nm) × Speed ​​(rpm) / 9.549.

Because of the difference between English and metric, the definition of horsepower is basically different. The imperial horsepower (hp) is defined as: a horse pulls a 165 ft. ft in a minute, equal to 33,000 lb-ft/min after multiplication; and metric horsepower (PS) The definition is that a horse pulls a 75kg object in 60 meters in one minute and multiplies it to 4500kg.gm/min.

After unit conversion, (1lb=0.454kg; 1ft=0.3048m), 1hp=4566kgm/min was found, which is slightly different from the metric 1PS=4500kg.gm/min, and if it is in watts (1W=1Nm/sec= 1/9.8kg.gm/sec), if you convert it, you can get 1hp=746W; 1ps=735W, two different results, about 1.5% difference.

Germany's DIN and the European Community's new standard EEC and Japan's JIS use the metric PS as the horsepower unit, while the SAE uses the British hp as the unit, but due to the advent of the world's integrated economy and to avoid complex conversions, The more original data has been changed to provide the undisputed international standard unit kilowatt kW as the power output of the engine.