What amount of energy is needed for an electron to jump from n = 1 to n = 4?

Aboxcar traveling at 12 m/s approaches a string of 5 identical boxcars sitting stationary on the track. the moving boxcar collides and links with the stationary cars and they all move off together along the track. what is the final speed of the cars immediately after the collision? (you may take the mass of each boxcar to be 18,537 kg.)

How does the amount of energy required to hold each proton and neutron in the nucleus compare to the energy released when they are removed?

Which situation will produce the greatest change of momentum