A train rolls past a stationary observer. To him, the train is moving at a speed of 25 m/s west, and a woman on the train is moving at a speed of 24.6 m/s west. How long does it take the woman to move 4 m relative to the train?

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?