Lesson 1 Oscillatory Motion

Translation motion Periodic motion

It is a Motion that is repeated in equal intervals of time Periodic motion

Oscillatory motion Wave motion

Defining the concept of Oscillatory motion Activity In SC. Book P 7

A pendulum It consists of a weight suspended on a rod, string or wire. When the weight is moved and let go, the pendulum will swing back and forth in a regular periodic motion.

observation 1) the oscillating body moves on both sides around its original position. the motion is repeated in equal time intervals 2) The displacement of the oscillating body around its rest point are equal 3) The velocity of the Oscillating body is maximum when it passes its original position and decrease gradually when it goes far from it.

A = rest point AC or AB = displacement

The periodic motion made by the oscillating body around its point of rest where the motion is repeated through equal intervals of time Oscillatory motion Oscillatory motion

what is the relation between the increase of the velocity of the pendulum and its kinetic energy? From your previous study the kinetic energy = ½ x mass x squared speed = ½ mV 2 kinetic energy increases increase So the kinetic energy increases when the velocity of the pendulum increase.

Exercise 1 page 8 Sc. book

Answer

The microwave oven A VIDEO CLIK TO PLAY Video

Graphical representation of the oscillatory motion Graphical representation of the oscillatory motion Activity 2 p 9 Activity 2 p 9 Observation : The pendulum draws the shape of the oscillatory motion on the paper tape as in the pictureConclusion: The simple harmonic motion is considered the simplest form of Oscillatory motion.

Some concepts related to the Oscillatory motion: Amplitude Complete Oscillation Periodic time frequency

Amplitude It is the maximum displacement achieved by oscillating body away from its point of rest it is measured in meter or centimeter AB, BA, AC, AC are amplitudes

Complete oscillation It is the movement made by the oscillating body when it passes a single point in its path of motion two consecutive times in the same direction In the figure : A complete oscillation can be written as the following : A BCA

Exercise 2 p 10 In which graph the amplitude is larger How many complete oscillation do exist between the points on both graphs (A) (B)

Answers Graph A has larger amplitude than B The number of complete oscillations in A is 3 complete oscillations The number of complete oscillations In B is 4 oscillations

Periodic time It is the time needed by oscillating body to make a complete oscillation it is measured by seconds. Periodic time (T) = Time Number of complete oscillation

Frequency it is the number of complete oscillation in one second Frequency (F) = Number of complete oscillation Time

the frequency is the reciprocal of periodic time Frequency (F) = Number of complete oscillation Time Periodic time (T) = Time Number of complete oscillation so frequency x periodic time = 1

what kind of mathematical relationship does this fig. represents? Frequency Periodic time The relation between the periodic time and the frequency is: inverse relation The frequency decrease by increasing the periodic time

Frequency is measured by : Hertz kilohertz = 1 x 10 3 hertz megahertz = 1 x 10 6 hertz gigahertz = 1 x 10 9 hertz

Exercise 4 p 11 Calculate the periodic time and frequency for an oscillating body that makes 300 complete oscillations in half a minute.

Answer: T = 0.5 x 60 = 30 sec. Periodic time = time / number of complete oscillation = 30/300 = 0.1 second Frequency = 1/T = 1/0.1 = 10 HZ