I would think that you would have to do 42/2=21Hz, but I'm not sure...
(a) The velocity of the object on the x-axis is 6 m/s, while on the y-axis is 2 m/s, so the magnitude of its velocity is the resultant of the velocities on the two axes:

And so, the kinetic energy of the object is

(b) The new velocity is 8.00 m/s on the x-axis and 4.00 m/s on the y-axis, so the magnitude of the new velocity is

And so the new kinetic energy is

So, the work done on the object is the variation of kinetic energy of the object:
Seismograph is the correct answer
Answer:
<u>Conservation</u>: using less water
<u>Xeriscaping</u>: replanting your yard with plants that do not require great amounts of water
<u>Desalination</u>: process of removing salt from water so that it can be used for consumption
<u>Water Budget</u>: finite amount of usable water available
<u>Potable</u>: water that is safe to use a drink