You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "in the universal law of gravitation what does the symbol r stand for?" whose answer is distance.
Each document should contain about 30 words, and these documents should contain useful information.

Query: what symbol is used for distance in the universal law of gravitation
Useful Output:

Doc 1: The force of attraction between any two unit masses separated by a unit distance is called the universal gravitational constant denoted by G
Doc 2:  distance between them. The symbol ɡ should not be confused with G, the gravitational constant, or g, the symbol for gram. The ɡ is also used
Doc 3: Gravitational constant (G), physical constant denoted by G and used in calculating the gravitational attraction between two objects.
Doc 4: In symbols, the magnitude of the attractive force F is equal to G (the gravitational constant, a number the size of which depends on the system
Doc 5: R, usually actually, lower case “r” is used since gravity problems are often solved most easily in spherical coordinates and “r” is how distance