Water enters a 180° elbow with an average velocity v1 = 3 m/s. the diameter at the inlet of the elbow is 6.0 cm and the exit diameter is 2.0 cm. the water exits to atmosphere. determine the magnitude of the horizontal force required to hold the elbow in place. (ignore the pressure component of the force.)

The nuclear potential that binds protons and neutrons in the nucleus of an atom is often approximated by a square well. imagine a proton conned in an innite square well of length 105 nm, a typical nuclear diameter. calculate the wavelength and energy associated with the photon that is emitted when the proton undergoes a transition from the rst excited state (n 2) to the ground state (n 1). in what region of the electromagnetic spectrum does this wavelength belong?