In a Harry Potter movie, there is a big pendulum in the Great Hall that
goes back and forth once every
18.9 s. What is the length of the
pendulum (if it obeys Physics
instead of magic)?

If steel is more dense that lake water, why can a boat float

The energy released by a nuclear fusion reaction is produced when

Amichelson interferometer operating at a 600 nm wavelength has a 3.02-cm-long glass cell in one arm. to begin, the air is pumped out of the cell and mirror m2 is adjusted to produce a bright spot at the center of the interference pattern. then a valve is opened and air is slowly admitted into the cell. the index of refraction of air at 1.00 atm pressure is 1.00028.how many bright-dark-bright fringe shifts are observed as the cell fills with air?