Energy

1
Energy Mass

• Nuclear Physics Lesson 12

2
Homework

• Research and explain how electron diffraction can
  be used to determine the radius of the nucleus (6
  Marks)
• Also complete nuclear radius sheet by Thursday.

3
Learning Objectives

• Know how the mass of an object changes as it
  gains energy.
• Know how to calculate the energy released in
  nuclear reactions.
• Know how to calculate the work done in removing a
  nucleon from the nucleus.

4
Einsteins Equation

• The mass of an object increases when it gains
  energy E, is accordance with this equation-
• Where m is the change of mass and c is the speed
  of light in a vacuum (3.00 108 m s-1).

5
Video

• Einsteins Equation of Life and Death Part 1 430
  to Part 2 140

6
Example

• A sealed torch radiates 10 W of light for 10
  hours, how much energy has been lost?
• By how much would the torchs mass decrease by?

7
Energy Changes in Reactions

• Reactions on the nuclear level do involve
  significant changes of mass.
• The energy released Q, from the difference ?m in
  mass before and after the reaction.
• Mass after the reaction is less than before ?
  converted to energy.

8
Example

• Polonium-210 is an alpha emitter. Write down the
  decay equation and calculated the energy released
  MeV.
• Mass of polonium-210 nucleus 209.93667 u
• Mass of lead-206 nucleus 205.92936 u
• Mass of alpha particle 4.00150 u