31. A hydrogen atom initially at rest and in its ground state absorbs a 100eV photon. If the ejected photoelectron moves in the same direction as the incident photon, find (a) the kinetic energy and speed of the photoelectron and (b) the momentum and energy of the recoiling proton

The experiment done in lab is repeated, using a ball that has unknown mass m. you plot your data in the form of f 2 versus m/l, with f in rev/s, m in kg, and l in m. your data falls close to a straight line that has slope 3.19 m/(kg · s2). use g = 9.80 m/s2 and calculate the mass m of the ball.