PHYSICS LAB EXPERIMENT
EXPERIMENT # 5
Velocity of a Pulse
Propagated Through a Slinky
Our Objective
To determine the
velocity of a pulse propagated through a slinky or a stretched string.
The Theory
What is meant by a slinky?
A slinky is a long
helical spring, usually made of steel. It is flexible and has appreciable
elasticity. It produces transverse waves when one end is fixed and the other
end is stretched and given a jerk at right angle to its length. It produces
longitudinal waves when compressions are given at regular intervals of time at
the free end of the slinky. A disturbance which propagates through a medium is
called wave.
What are longitudinal waves?
In case of longitudinal
waves, the particles of the medium vibrate to and fro periodically along the
direction of propagation of the wave. It consists of alternate compressions and
rarefactions. For example, waves along a compressed spring are longitudinal
waves.
Wavelength
(λ) of longitudinal waves
can be defined as:
The distance covered by one complete rarefaction and one complete compression. [Or] The distance between two consecutive compressions or rarefactions.
The distance covered by one complete rarefaction and one complete compression. [Or] The distance between two consecutive compressions or rarefactions.
Frequency:
The number of vibrations made by a particle in the slinky per unit time (one
second) is called its frequency. It is denoted by the symbol ‘f’.
Materials Required:
Procedure:
For Transverse Waves
1.
Take a slinky and place
it lengthwise on the smooth surface of the table.
2.
Tie one end of the
slinky with the fixed hook.
3.
Hold the free end of the
slinky and stretch it (1 to 3 m depending upon the nature of slinky).
4.
Move your hand
periodically and uniformly at right angles to the length of the slinky.
5.
Observe the propagation
of the wave through the slinky and observe the formation of crests and
troughs.
For Longitudinal Waves
6.
Compress the free end of
the slinky periodically and observe the slinky.
Did you see an alternate compressions and rarefactions passing
through the slinky?
7.
Measure the wavelength
by measuring the distance between two consecutive troughs (T and T) or two
crests (C and C) in case of transverse wave. In case of longitudinal wave, λ is
equal to distance between two consecutive compressions (C and C) or
rarefactions (R and R).
8.
Note the time as pulse
(wave) passes through slinky for a particular distance from which we can find
out the velocity of the wave.
Calculations:
VELOCITY, V = DISTANCE TRAVELLED / TIME
TAKEN
Observations:
Length of slinky (cm)
|
Distance travelled by
the pulse (cm )
|
Distance travelled by
the pulse (m)
|
Time (s)
|
Velocity =
Distance/time (m/s)
|
500
|
500
|
5
|
4.6
|
1.06
|
300
|
300
|
3
|
2.8
|
1.07
|
Result:
The velocity of a pulse
(wave) propagated through a stretched slinky = 1.06 m/s
Precautions:
1.
The slinky should have
appropriate length, elasticity and flexibility.
2.
One end of the slinky
should be fixed properly.
3.
The top of the table
should be smooth.
