Water flows at speed v in a pipe of radius r. Neglecting viscosity, at what speed does the water flow through a constriction in which the radius of the pipe is r/3

9v

Explanation:

Given that the water flows at speed v in a pipe of radius r.

Let is the speed of water flow where the radius of the pipe is r/3.

By using the continuity equation, the mass flow rate of water is the same at all the cross-sections of the pipe, wh have

Where and are the density, area of the cross-section and speed at cross-section 1 and   and are the density, area of the cross-section and speed at cross-section 2.

As the density of the water remains constant. so .

Hence, the speed of the water flow where the radius is r/3 is .

answer: cesare beccaria developed the classical school of criminology with from philosopher jeremy bentham

explanation:

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.