Unit conversion in the second year of junior high school The unit conversion of physics is expressed by scientific counting method. I also know the rate of progress, but I never change the conversion Example: 200km = 2.01 * 10 to the fifth power, M = 2.0 * 10 to the seventh power, cm How to calculate? I know how to use the large to reduce the multiplication rate and the small to large division rate. But I still don't know how to use the scientific counting method to express the conversion unit It was originally 200km. Why should it be changed to the quintic m of 2.01 * 10 when changing the unit Depressed!

Unit conversion in the second year of junior high school The unit conversion of physics is expressed by scientific counting method. I also know the rate of progress, but I never change the conversion Example: 200km = 2.01 * 10 to the fifth power, M = 2.0 * 10 to the seventh power, cm How to calculate? I know how to use the large to reduce the multiplication rate and the small to large division rate. But I still don't know how to use the scientific counting method to express the conversion unit It was originally 200km. Why should it be changed to the quintic m of 2.01 * 10 when changing the unit Depressed!

It's very simple! Using scientific counting method is to make the digital record more concise and clear
The exact number of digits to remember: two or three, depending on the subject requirements
In addition, unit conversion:
Take one place after the precise decimal point as an example
1km = 1000m = cubic meter of 1.0x10
10km = 10x1000m = the fourth power of 1.0x10 (the first power of 10 and the third power of X10 are equal to the fourth power of 10, that is, the fourth power of 1.0x10)
Remember to add exponentially when multiplying and subtract exponentially when dividing. Remember the exact number of digits!

The following unit conversion format is correct
A.1.80m=1.80×100cm=180cm
B.1.80m=1.80m×100cm=180cm
C.1.80m=1.80×100=180cm
D.1.80m=1.80cm×100=180cm

A is right
B error. Multiplication of two lengths yields a unit of area
C error. Multiplication of two numbers without unit
D error. When calculating with unit in physical operation, when encountering unit mutualization, the unit should be brought last

The unit conversion of physics is expressed by scientific counting method. I also know the rate of progress, but I never change the conversion
Example: 200km = 2.01 * 10 to the fifth power, M = 2.0 * 10 to the seventh power, cm
How to calculate? I know how to use the large to reduce the multiplication rate and the small to large division rate. But I still don't know how to use the scientific counting method to express the conversion unit
It was originally 200km. Why should it be changed to the quintic m of 2.01 * 10 when changing the unit

The power of 10 means that there are several zeros after 1. For example, the fifth power of 10 means 100000
K is 1000, so it's the third power of 10
So 200 km = 200 * 1000 m = 200 * 10 to the third power, I give two zeros in 200 to the back, that is 2 * 10 to the fifth power
It can also be understood in this way
The quintic power of 200km = 200 * 1000m = 200000m = 2 * 10 (five zeros)

Complete the following speed unit conversion
(1)18km/h=______ m/s (2)10m/s=______ km/h
(3)50cm/s=______ km/h (4)30dm/s=______ km/h

5 36
1.8 10.8
Well, you have to know the meaning of 18km / h: it means to walk 18 km in an hour, that is 18000 meters, then 18000 divided by 3600 meters in one second, the number is 5, so it is 5m / s
Similarly, 10m / s means walking 10 meters in one second, then walking 36000 meters in one hour, that is 36 kilometers, that is 36 km / h