Roger sees water balloons fall past his window. he notices that each balloon strikes the sidewalk 1.2s after passing his window. roger's room is on the fifth floor, 25m above the sidewalk.
how fast are the balloons traveling when they pass roger's window? assuming the balloons are being released from rest, from what floor are they being released? each floor of the dorm is 5.0 m high.

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?