Two violins,viola and violoncello
1st violin 2nd violin Viola Cello
Two violins, violist and cellist
Two violins, a viola and a cello is the standard.
Generally, a string quartet consists of two violins, a viola, and a cello. However, a quartet can be made up of all sorts of variations on this model.
You can get used string instruments from countless local music shops. If you use google maps you can find a very long list of the shops nearest you.
a violin, viola and a cello or two violins and a cello
You would find violins, cellos and maybe a Double Bass.
Traditionally, we can find a violin, cello, viola, and bass used in an orchestral arrangement.
The circumference of any circle is the distance around the outside. You can take a piece of string and measure the outside of the quarter. See how much string fits around the outside. Then put that length of string up against the edge of a ruler and see how long it is.
I would look for a store, maybe in a big city, that specializes in banjos and acoustic string instruments, and give them a call.
To find the density of a quarter, you would first measure its mass using a scale. Then, you would measure its volume by water displacement, where you would measure the amount of water the quarter displaces when submerged. Finally, divide the mass by the volume to calculate the density of the quarter.
Look in the volume with U in it. It may cross reference to an entry on musical instruments or string instruments. Most encyclopedias will have an index that can give you the actual page for the entry.