Just as there are atomic shell features, there are alsonuclear shell structures. Certain values of the numberof protons Z and neutrons N are called magic, becausecertain nuclides with these magic numbers aremore tightly bound and have enhanced abundances.These numbers are 2, 8, 20, 28, 50, 82, and 126. (a) Usethis fact to explain why 4He and 16O have peaks in thebinding energy curve of Figure 12.7. (b) Explain why208Pb is one of the heaviest stable nuclides. (c) Discussthe abundances of the calcium isotopes with respect totheir value of N. The German physicists Maria Goeppert-Mayerand J. Hans D. Jensen won the Nobel Prizein Physics in 1963 for their discoveries concerning thenuclear shell model

Work and Power Work ● When a force acts on an object, i does work on the object. ○ W=F*d ○ Work = Force * isplacement ■ The force must be PARALLEL to the displacement ● Measured in Joules (Newtonmeter) ● Ifthere is an angle, only the cosine of the angle times the force is what i doing the work. Sine of the angle times the force is doing nothing. ● Ifsomething lides on a amp, W=mgdsinθ ○ Decreasing the angle will decrease the ork ● Ifthere is more than one force acting on an object, we can find the work done by each force then determine the net force which provides the total work. W=Fd=(Force of man on fridge Force of friction) ● Positive work Zero ork Negative work Work Example More ork ● Positive work i ncreases speed ● Negative work ecreases speed ● Zero work has no effect on peed. ○ Falling object positive ○ Throwing object up egative ○ Throwing object to side zero Work Done by a Variable Force ● Work is also the area underneath the gra