Exercises 1 What is the energy associated with the fifth orbit? b. Calculate the radius of Bohr's fifth orbit for a hydrogen atom.
2 A hydrogen atom makes a transition from the n = 3 level to the n = 2 level. What is the change in energy?
3 An electron is in the second excited orbit of hydrogen, corresponding to n = 3.
Find (a) the radius of the orbit and (b) the wavelength of the electron in this orbit.​

Two cannon balls weighing 18 kg and 24 kg are chained together and fired horizontally with a velocity of 165 m/s from the top of a 21-m wall. the chain breaks during the flight of the cannonballs and the 18-kg cannonball strikes the ground at t = 1.5 s, at a distance of 240 m from the foot of the wall, and 7 m to the right of the line of fire. determine the position of the other cannonball at that instant. neglect the resistance of the air.