3.1 Oscillations

1
3.1 Oscillations
Make a list of things which oscillate or vibrate
tides
Describe what happens to the displacement from
the equilibrium position when the mass is
raised up 2 cm and let go
Mass on a spring
pendulum
Sun spot activity
Skate boarder in a half pipe
2
3.1 Oscillations
Make a list of things which oscillate or vibrate
tides
Describe what happens to the displacement from
the equilibrium position when the mass is
raised up 2 cm and let go
Mass on a spring
pendulum
Sun spot activity
Skate boarder in a half pipe
2 cm
Equilibrium position
3
3.1 Oscillations
The displacement
1. Decreases while going down
Describe what happens to the displacement from
the equilibrium position when the mass is
raised up 2 cm and let go
2. Increases while going down
3. Decreases while going up
4. Increases while going up
2 cm
Equilibrium position
4
Amplitude max displacement from equilibrium
( m)
Free oscillations occur when no friction is
present, so amplitude is constant
Time period T time for one complete oscillation
( seconds)
Frequency the number of complete oscillations
each second ( Hertz)
Angular frequency w the number of radians each
second ( rad/sec) w 2 p


T
http//www.stmary.ws/highschool/physics/home/notes
/waves/default.htm
5
Remember
Remember T 1 f
1. Calculate T/s if f 50 Hz
2. Calculate T/s if f 500 M Hz
6
Remember
Remember T 1 f
1. Calculate T/s if f 50 Hz
T 1
0.02 s 50
2. Calculate T/s if f 500 M Hz
7
Remember
Remember T 1 f
1. Calculate T/s if f 50 Hz
T 1
0.02 s 50
2. Calculate T/s if f 500 M Hz
T 1 2
x10 - 8 s
50x106
Remember w 2 p f
3. Calculate w / rads-1 for the above
8
B
C
A
B
9
B
C
A
B
10
Red lags behind green
PHASE DIFFERENCE
11
Red lags behind green
PHASE DIFFERENCE
0.6
1.2
1.8
2.4
time/s
?t
12
Red lags behind green
Fraction of period out of phase
t T T
0.6
1.2
1.8
2.4
time/s
?t
13
Red lags behind green
Fraction of period out of phase
t T 0.6 T T
2.4
Phase difference in radians 2 p
t T
0.6
1.2
1.8
2.4
time/s
?t
14
Red lags behind green
Fraction of period out of phase
t T 0.6 T T
T 2.4 4
Phase difference in radians 2 p
t T
0.6
1.2
1.8
2.4
time/s
?t
15
Red lags behind green
Fraction of period out of phase
t T 0.6 T T
T 2.4 4
Phase difference in radians 2 p
t T
T 2.4 seconds for both children on their
swings But the red one lags behind the green by
0.6 sec 0.6 T or ¼ T
2.4 Phase difference in radians 2 p 0.6

2.4
2 p p rad
4
2
0.6
1.2
1.8
2.4
time/s
?t
16
Red lags behind green
Fraction of period out of phase
t T 0.6 T T
T 2.4 4
Phase difference in radians 2 p
t T
T 2.4 seconds for both children on their
swings But the red one lags behind the green by
0.6 sec 0.6 T or ¼ T
2.4 Phase difference in radians 2 p 0.6

2.4
2 p p rad
4
2
0.6
1.2
1.8
2.4
time/s
?t
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