Download Oscillatory Motion

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}
•
•
•
•
•
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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 2cm
The maximum displacement away from its original position is
2cm
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