Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point
Amplitude: the maximum displacement of a wave from its undisturbed ( equilibrium) position
Frequency: the
number of waves passing a given point in a second
Frequency is the inverse
of the wave’s time period
Period: time for a particle on a medium to make one
complete vibrational cycle
Formula:
Question no. 1
The time needed to
complete 300 vibrations is 1 minute. Calculate :
a.
Its time-Period
b.
Its frequency
Answer :
a.
T = t : n
T = 60s : 300 = 0.2 s
b.
f = n : t
f = 300 : 60 = 5 Hz
Question no. 2
An object vibrates 100
times in 25 s. Calculate :
a.
Its time-Period
b.
Its frequency
Answer :
a.
T = t : n
T = 25s : 100 = 0.25 s
b.
f = n : t
f = 100 : 25 = 4 Hz
Question no. 3
An object vibrates 100
times in 25 s. How many vibrations will happen in 2
minutes?
Answer :
T1
= T2
t1
: n1 = t2 : n2
25 s : 100
= 120 : n2
n2
= 4 x 120 = 480 times
Question no. 4
An object vibrates 120
times in 1 minute. How many vibrations will happen in 2
hours?
Answer :
T1
= T2
t1
: n1 = t2 : n2
1 minute :
100 = 120 minutes : n2
n2
= 100 x 120 = 12000 times
Question no. 5
Look at the figure below.
The distance from A to C is 6 cm. the time needed from A to C is 0.4 second. Calculate :
a.
its amplitude
b.
its time-period
c.
its frequency
Answer:
a.
Amplitude = distance A-B
= 6 cm : 2 = 3 cm
b.
T = t : n = 0.4 s : 0.5 =
0.8 s
c.
f = n : t = 0.5 : 0.4s =
1.25 Hz
Question no. 6
Look at the figure below!
a. which pendulum above has the greatest time-period?
b. which
pendulum above has the greatest frequency?
Answer :
a. The greatest time-period : figure S
b.
The greatest frequency:
figure P
