For a very rough pipe wall the friction factor is constant at high reynolds numbers. for a length l1 the pressure drop over the length is p1. if the length of the pipe is then doubled, what is the relation of the new pressure drop p2 to the original pressure drop p1 at the original mass flow rate?

the answer is c. natural gas because both a and b are their own forms of energy.

from our point of view here on the surface, the 'ecliptic' is the apparent path of the sun through the constellations of the zodiac in the course of a year. (d)

an isotope is an atom with a different number of neutrons than another atom of the same element. since atoms of the same element all have the same number of protons, choice b(6pro & 6neu vs. 6pro& 7neu) is an example of isotopes

1. the positioning of the sun

2. equinox

3. summer solstice