An object is dropped from the top of a building and strikes the ground 2.Os later. How tall is the building?

What would the difference of spectral lines emitted by hydrogen gas in distant galaxies which is normally found at a wavelength of 21 cm on earth, be observed at 21.1 centimeters?

Which compound is held together by the electrostatic force between two ions? a. co2 b. cci4 c. h2s d. mgf2

Acid precipitation chemically weathering a 5.0-kg limestone rock . which coukd be the result ?