1 means positive and negative, for example, 2 means positive and negative 2.
2, used for addition and subtraction, such as 10 2, used for 10+2 and 10-2, which are common in the net weight of commodity packaging.
Extended data:
Symbol is not a single concept in middle school physics. It can be used to represent the positive and negative of rational numbers, as well as the nature and direction of physical quantities. The situation is more complicated. When students reach the final stage of high school, with the accumulation of knowledge, they often form negative migration, which leads to many mistakes in both positive and negative aspects of physical quantities. There are the following manifestations:
1, simply understand the positive and negative of physics as the positive and negative of rational numbers, such as "speed -3m/s is less than speed 1m/s".
2. Unclear understanding of the meaning of physical quantity symbols leads to errors, such as thinking that "the positive work direction is opposite to the negative work direction".
3. Not understanding the connotation of physical concepts leads to the wrong judgment of symbols. For example, it is considered that "positive electric potential energy must be positive and negative electric potential energy must be negative".
The meaning of symbols is equal to the scalar of rational numbers: gravitational potential energy, electric potential energy and electric potential energy are positive and negative, and their determination is related to the zero potential point we choose, indicating whether they are big or small relative to the zero potential surface, and their absolute values indicate how big or small they are relative to the zero potential surface, so their size judgment is equivalent to rational numbers. For example, it can be considered that the gravitational potential energy of -3J is less than1j; The potential of -3v is less than that of-1v.