We know that frequency is an inverse value of time 
this implies that time is the inverse value of frequency 
.
Now since <em>f</em> is <em>40kHz</em><em>,</em><em> </em>we can calculate period or duration for that matter time.
Hope this helps.
r3t40
Eris is slightly more massive than Pluto. However, both of them are smaller than Earth's Moon.
This should conclude that Eris is a dwarf planet.
(1.6 x 10⁻¹⁹ C) x (300 N/C) = <em>4.8 x 10⁻¹⁷ Newton</em>
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C. 32400 because 540 * 60 = 32400
I believe (D) during the second half of the trampoline's movement downward and the first half of the trampoline's movement upward.
But this question is hard to answer. So it can also be C.
