A hydrometer is an instrument used to determine liquid density. A simple one is sketched in the figure below. The bulb of a syringe is squeezed and released to lift a sample of the liquid of interest into a tube containing a calibrated rod of known density. (Assume the rod is cylindrical.) The rod, of length L and average density 0, floats partially immersed in the liquid of density . A length h of the rod protrudes above the surface of the liquid. Show that the density of the liquid is given by =
0L
L − h
.
(Do this on paper. Your instructor may ask you to turn in this work.)

Assume that two of the electrons at the negative terminal have attached themselves to a nearby neutral atom. there is now a negative ion with a charge -2e at this terminal. what are the electric potential and electric potential energy of the negative ion relative to the electron? the electric potential and the electric potential energy are both twice as much. the electric potential is twice as much and the electric potential energy is the same. the electric potential is the same and the electric potential energy is twice as much. the electric potential and the electric potential energy are both the same. the electric potential is the same and the electric potential energy is increased by the mass ratio of the oxygen ion to the electron. the electric potential is twice as much and the electric potential energy is increased by the mass ratio of the oxygen ion to the electron.