What is used to create the vibrations?
a vibration generator, connected to a singal detector
What is used to secure
string is thread through the vibration generator to a retort stand
the retort stand is held by a counterweight
the other end of the string is held against a moveable bride
it is then attached to mass on a pulley clamped to the bench
What are the control measured?
- leave the signal generator on for 20 minutes, in order for the frequency to stabalise
- the ouput power should be turned up to a value which gives steady vibraation
- the bridge should be at the same height as the hole
What is the independant variable?
the length of the distance between the vibration generator and the position of the bridge
What is the dependent variable?
the freuquency of the resonations
how is the frequency found?
frequency of the signal generator from zero until the string resonates at its fundemental frequency
(node at each end and a central antinode)
How are the results made more reliable?
repeats, find the mean value
if you didnt get this :
What graph is plotted?
1/f against length
What is the gradient?
should be a straight line through the origin
c = fλ = 2fL (at fundemental node)
the gradient is 1 / fl
so c is giv en by 2 / gradient in ms-1
What are the alternatives to this technique?
different masses hanging on the string
different thickness of string
to investigate the ffect of changing tension and mass of the string
How is speed found from tension and mass?
c = √ ( T / m )
m = mass per unit of length ( kgm-1)
What effect does doubling the fundemental frequency while keeping l, T and m constant?
causes teh string to resonate in its second harmonic
(nodes at either end, a central node, and two antinodes)