A boy pushes a 35 kg table with rubber padding under the legs across a dry concrete floor. How much force does the boy need to continue
applying to keep pushing the table? The kinetic friction coefficient is 0.8.
0 272 N
429 N
28 N

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?