Adolphin emits ultrasound at 100khz and uses the timing of reflections to determine the position of objects in the water.

what is the wavelength of this ultrasound? assume that temperature of water is 20 degrees c. answer in cm

The speed of a wave (the sound in this case) is given by the following formula:

  (1)

Where:

is the frequency

the wavelength

It is known that the speed of sound in water at is:

So, we only have to find  from (1):

  (2)

Knowing :

But we were asked to find the wavelength in cm and we have to make the conversion:

Hence:

unlike poles attract

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

where is unknown. because the position is parabolic, there is symmetry about the midpoint at , and we know that

so that the position function is

which means the velocity is

then the total distance traveled is

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at and ends at , so its displacement is 0.