Undoubtedly, your grade school grammar teacher has scolded you at one point or another for your inadvertent use of a double negative. Statements such as “I don’t know nothing about physics”, while grammatically incorrect, are often semantically inaccurate as well. While the previous statement would commonly be understood to mean the person possesses no knowledge of physics, the actual statement implies the opposite, that the preposition “I know nothing about physics” is incorrect. Certainly your teacher offered sound advice and one would be wise to heed such instruction.