Chapter 15 oscillations20183.ppt

Review : Chap.12 Example 12-4，5, 6 Preview ：Chap.13, 14 Let students Give more vibrate in nature. TB. 1st p, the term simple refers to the absence of external force of system such as : friction or viscosity. The word harmonic refers to music: musical instruments generally vibrate harmonically. These three function are all the solution of motion equation,. These three function are all the solution of motion equation,. The third form is a general one, it include two other forms : it can be rewritten as x=A’cos(ωt+φ), or x=A’sin (ωt+φ’) These three function are all the solution of motion equation,. These three function are all the solution of motion equation,. The third form is a general one, it include two other forms : it can be rewritten as x=A’cos(ωt+φ), or x=A’sin (ωt+φ’) TB. Question 4,5 P318 12-20 A 450-g object oscillates from a vertically hanging light spring once every 0.55s. (a) write down the equation giving its position y (+upward) as a function of time t, assuming is started by being compressed 10cm from the equilibrium position (where y=0),and released. (b) how long will it take to get to the equilibrium position for the first time? (c) what will be its maximum speed? (d) what will be its maximum acceleration, and where will it first be attained? y Solution: 质点的运动方程： Equilibrium position At position y y Solution: 质点的运动方程： P323 12-81 A mass m is gently placed on the end of a freely hanging spring. The mass then falls 22.0 cm before it stops and begins to rise. What is the frequency of the oscillation? Solution: Two equal masses m lying on a frictionless horizontal surface are attached to each other by a spring of spring constant k as shown. The spring is compressed a distance ?x, and then both masses are released from rest at the same instant. (a) What is the maximum speed of masses? (b) What is the period of oscillation of each mass? The same experiment is then performed with the difference that the two blocks attached to