医学物理学 General Review .ppt

General Review for first four Chapters With examples and problem solutions A. Review to Chapter 1 B. Review to Chapter 2 C. Review to Chapter 3 D. Review to Chapter 4 1 Simple harmonic motion Simple harmonic force; equation of SHM; speed and acceleration of vibration, characteristic quantities of SHM; the energy of SHM, total energy of SHM is conserved. Example 4-1. For the sinusoidal motion shown, give the amplitude, period, frequency, initial phase, and the vibrational equation. t Example 4-2. If a 2.0 kg mass vibrates at the end of a spring according to the relation y = 0.2 cos(9.42t) m, find the following: (a) amplitude of vibration, (b) frequency of vibration, ? spring constant, and (d) maximum speed of the mass. Solution: A = 0.2m, f = ?/2? = 1.5 Hz， k= ?2/m= 180 (N/m) v=dy/dt = 1.88m/s Example 4-3. for the SHM system, its energy is conserved! (1) What is the energy if its amplitude is A? (2) what is the total energy expression in other positions? Solution: (1)= LHS; (2) = RHS Speed in SHM can be determined via the above energy equation as The is another formula for calculating the speed of a SHM. Example 4-4 A 200g mass vibrates horizontally without friction at the end of a horizontal spring for which k =7.0N/m. the mass is displaced 5.0cm from equilibrium and released. Find (a) its maximum speed and (b) its speed when it is 3.0cm from equilibrium. (c) what is its acceleration in each of these case? Solution: hints: both ways are OK: (1) set up the equation of motion; (2) use the formulae you know. Damped harmonic motion, forced vibration and resonance characteristics of damped vibration (period, mechanical energy, frequency, amplitude) characteristics of forced vibration and resonance What condition for a vibrational system can cause the resonance to happen ? * Fundamental physical quantities and their units (Time (s), Length (m), Mass (kg), Electric current (Ampere, A), Temperature (Kelvin, K), Amount of substance (mole,