D is the correct answer!!
Answer:
5.62 m/s
Explanation:
Newton's law of motion can be used to determine the maximum speed of the elevator. In the question, we are given:
Force exerted by the elevator (R) = 1.7 times the weight of the passenger (m*g)
Thus: R = 1.7*m*g
Distance (s) = 2.3 m
Newton's second law of motion: R - m*g = m*a
1.7*m*g - m*g = m*a
a = 0.7*m*g/m = 0.7*g = 0.7*9.8 = 6.86 m/s²
To determine the maximum speed:



Therefore, the elevator maximum speed is equivalent to 5.62 m/s.
Displacement is d
Vf² = Vi² + 2 g d
(-20²) = (+10²) + 2 (-9.8) d
-19.6 d = 300
d = -15.3 m
negative means lower
time is t
d = Vi t + 1/2 g t²
-15.3 = 10 t + (-4.9) t²
4.9 t² - 10 t -15.3 = 0
t = 3.06 s
Hope this helps -John
To solve this problem we will apply the concepts related to wavelength, as well as Rayleigh's Criterion or Optical resolution, the optical limit due to diffraction can be calculated empirically from the following relationship,

Here,
= Wavelength
d= Diameter of aperture
= Angular resolution or diffraction angle
Our values are given as,

The frequency of the sound is 
The speed of the sound is 
The wavelength of the sound is

Here,
v = Velocity of the wave
f = Frequency
Replacing,


The diffraction condition is then,

Replacing,

d = 0.24 m
Therefore the diameter should be 0.24m