The dumbwaiter d and its load have a combined weight of 600 lb, while the counterweight c weighs 800 lb. determine the power delivered by the electric motor m when the dumbwaiter (a) is moving up at a constant speed of 8 ft/s, (b) has an instantaneous velocity of 8 ft/s and an acceleration of 2.5 ft/s2, both directed upward

a) 2.91 hp

b) 3.81 hp

Explanation:

As we cans ee in the diagram given below force F has same direction as velocity , The power is equivalent to

A) Uniform motion

As both bodies are in equilibrium,therefore we have following relation

By free body for C:

2T - 800 = 0

T = 400 lb

By free body for D

F + T - 600 lb = 0

F = 600 - T

  = 600 - 400 = 200 lb

2)

we have

from equation of motion

by free body diagram C

F = ma

T = 384.5 lb

by free body diagram of D

F = ma

F =262.1 lb

the answer would most likely be c, because if it's a comical piece of information, it may likely not be true, if it's a site that allows anybody to edit the content, it could mean a five year old is typing the info, and if it's a tv show produced by a celeb, it may have a biased opinion.

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.