Apendulum bob is released from some initial height such that the speed of the bob at the bottom of the swing is 2.7 m/s. the acceleration of gravity is 9.81 m/s^2. what is the initial height of the bob? answer in units of m.

Potential energy is the energy possessed by a body while at rest while kinetic energy possessed by a body in motion. In this case the energy of the bob at the highest point is the potential energy while the energy possessed by the bob at the lowest point is the kinetic energy. The potential energy is converted to kinetic energy while the bob sets in motion . Therefore;
      1/2mv²=mgh
     = 1/2 v² =gh
       1/2× 2.7² = 9.81 h
          h = 0.372 m

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -