semiconductors ... silicon, germanium etc ...
The rate of change of d(t) at t = 2 and t = 6 is the ratio between the change of distance (difference between the distances) to the time elapsed. That is,
r = (576 - 64) / (6 - 2) = 128 ft /s
The rate of change is equal to 128 ft/s and this represents the average speed at this time interval.
The wavelength<span> in a </span>longitudinal wave<span> is probably the distance between two consecutive compressions or between two consecutive rarefactions. The amplitude is the maximum displacement from equilibrium. ... The amplitude is the distance from the equilibrium position of the medium to a compression or a rarefaction.</span>
Answer:410 Hz
Explanation:
It is given that frequency of tuning fork is 415 Hz and hears a beat of 5 beat per second
so untuned frequency must be either 410 Hz or 420 Hz because beat frequency is the difference in frequency of two notes.
When she tightens the string the beat frequency decrease
and velocity 
where 



where T=tension
it T increase v also increases and from 1 st equation frequency is also increasing therefore untuned frequency must be 410 Hz because beat frequency is decreasing.