There is a road that starts from point A 10 Km east to point B, 5 Km south to point C, 10 Km west to point D, and 5 Km north back to point A. What is
your distance if you travel from point A to point B, to point C?*

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?

Can somebody explain to me how newton's 3rd law relates to momentum? ~ap physics 1

Consider an insulating crystal, made up of layers of atoms. what form would you expect the temperature dependence of the phonon heat capacity to approach at extremely low temperatures if the interlayer coupling is i)very strong (rigid coupling), and ii) very weak. explain.