What does the big ‘2’ in 2CO2 mean?

Please help quickly i'm in science class

Tall pacific coast redwood trees can reach heights of about 100 m. if air drag is negligibly small, how fast is a sequola cone moving when it reaches the ground f it dropped from the top of a 100 m tree?

Which sound characteristic is not affected by the relative motion of an object

Which basic property determines a colored light's placement on the spectrum of visible light? a. speed b. frequency c. amplitude d. velocity