Q. A 110 kg clock initially at rest on a horizontal floor requires a 607 N horizontal force to set it in motion. After the clock is in motion, a horizontal force of 525 N keeps it moving with a constant velocity.
Q. Two parallel slits are illuminated by light composed of two wavelengths, one of which is 645 nm. On a viewing screen, the light whose wavelength is known produces its sixth dark fringe at the same place where the light whose wavelength is unknown produces its fourth-order bright fringe. The fringes are counted relative to the central or zeroth-order bright fringe. What is the unknown wavelength?