Jack and Jill are pushing a 3 kg object on a rough surface; the object accelerates at a rate of 5 m/s2. Calculate the force applied by the Jack knowing that Jill is pushing 4 N and the rough surface applies 2 N force on the box as friction 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?