Lesson01_1

Lesson01_1 - Lesson 01 From Modern Physics to Radiation...

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Unformatted text preview: Lesson 01 From Modern Physics to Radiation Physics MP 200 Radiation Physics- 2010 Duke Medical Physics Graduate Program 1 Introduction In order to study Radiation Physics in detail, we need a knowledge of: • Classical mechanics, • Special theory of relativity and, • Quantum physics. In this lesson, we briefly cover the some of the materials that we need to understand the Radiation Physics. Revision of Classical Mechanics • Subject that developed by Isaac Newton and other contemporary physicists. • Related to objects moving with speeds <<< speed of light. • Governed by Newton’s Laws of Motion Newtons Laws of Motion • First Law: Law of inertia In the Absence of a net force, a body at rest remains at rest, and a body in motion remains in motion with constant velocity. • Second Law: Net force acting on a body or system is proportional to the rate of change of momentum of the body ( system) F = dp dt If mass m is constant, F = m dv dt = ma 2 • Third Law: For every force(action), there is an equal and opposite force(reaction). Work and Energy • For a constant force F , work, W = F.d . where d = distance • For a variable force, W = R F ( r ) .dr • Kinetic energy K = 1 2 mv 2 and potential energy U = mgh h = height from a reference point • Work energy theorem: W = K f- K = Δ K K = kinetic energy Conservative and Non-conservative forces • Conservative Force: Work done by the force in moving an object is independent of the objects path. example: gravitational force • Non-conservative Force: Work done by the force, in moving an object depends on the ob- jects path. example: frictional force Conservation of Mechanical energy The sum of kinetic energy ( K ) and potential energy ( V ) is called total mechanical energy. 3 For a conservative system, the sum of all kinetic and potential energy is constant, and equals the total mechanical energy of the system. Final total mechanical energy = Initial total mechanical energy 1 2 mv 2 + V = 1 2 mv 2 + V Isolated system and law of conservation of energy • In a closed system or an isolated system, particles can interact with each other, but not with anything outside. • The Law of conservation of total energy: The total energy of an isolated system is always conserved. Power The time rate of doing work is called power. P = W t units: J.s- 1 and 1 J.s- 1 = 1 Watt Momentum • Linear Momentum p = mv , is a vector quantity. Units: kg.m.s- 1 • Conservation of linear momentum: For an isolated system, linear momentum is conserved. i.e. Final linear momentum of the system = Initial linear momen- tum p f = p i 4 Revision of Special Theory of Relativity • Event: A Physical happening that occurs at a certain place and time....
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This note was uploaded on 10/30/2010 for the course MP 200 taught by Professor Guna during the Fall '10 term at Duke.

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Lesson01_1 - Lesson 01 From Modern Physics to Radiation...

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