Oscillatory Motion Lesson 1 Unit 1 Prep 2

Oscillatory Motion Lesson (1) Unit (1) Prep (2) Made by: Dr. Niveen Fawzy

Motion & its types • Motion: It’s the change in an object’s position as time passes. • Types of motion • 1 - Translational motion • 2 - Periodic motion • First Translational motion • Its the motion in which the object’s position is changed relative to a fixed point (or a fixed frame of reference) from time to time between initial & final positions

Examples on translational motion A person’s motion A car’s motion A bicycle’s motion Train’s motion

Second: Periodic motion • It’s a motion which is repeated regularly in equal periods of time {moves periodically back & forth over the same path } • N. B : It doesn’t have initial & final positions • Examples of periodic motion 1 -Oscillatory(vibrational) motion 2 - Circular motion 3 - Wave motion

Concept of Oscillatory Motion Steps: -Push with your hand gently the pendulum & leave it &use stopwatch to record time taken by pendulum to repeat its movement several times Observation: It will move on both sides around its original position (A) The displacement of oscillating body around its original position are equal This motion is repeated in equal time interval -Maximum velocity is at point (A) & decreases gradually when it goes away from point (A), so maximum KE at point (A) Conclusion The oscillatory body moves around its rest point & repeated at equal time intervals

Oscillatory motion •

• Note that: The movement of earth’s crust during earthquakes is considered an oscillatory motion While , The motion of rotary bee is a periodic motion but not considered an oscillatory motion because its not repeated on the 2 sides of its rest point Application for oscillatory motion Microwave oven: Its function depend on the vibration of water molecules in food by effect of microwaves. This oscillatory motion causes the collision of water molecules & this increases its heat Energy in very short time so food is cooked faster

Give reason • Food must be put in glass , pottery or ceramic pots while metallic pots are not used • Because metallic pots reflect microwaves

Graphical representation of oscillatory motion Tools: -Spring -weight-holder-pencil Steps: 1 - Fix pencil to weight , then tie one end to spring 2 - let the pencil’s tip touch the mid point of paper tape 3 -Roll the paper tape regularly , pull the weight downwards & leave it Observation: The pencil draws the shape of oscillatory motion Conclusion: The simple harmonic motion is the simplest oscillatory motion

The concepts related to oscillatory motion • 1 - Amplitude 2 - Complete oscillation • 3 - Periodic time 4 - Frequency • First: Amplitude • It’s the maximum displacement done by the oscillating body away from its original position {How far away an • • • oscillating body can get from center} Maximum displacement in a pendulum: AB = BA = BC = CB Each of them is an amplitude Measuring unit (cm) or (m) What is meant by: The amplitude of an oscillating body is 2 cm The maximum displacement away from its original position is 2 cm

Second: Complete oscillation •

Third: Periodic time •

Fourth: Frequency: •

Problems : •

Problem : •

Problems: •

Model answers of book lesson(1) unit(1) •

• Question (5): • X is the motion of string • Y is the motion of spring • Z is the motion of pendulum