Two ponies of equal mass are initially at diametrically opposite points on the rim of a large horizontal turntable that is turning freely on a vertical, frictionless axle through its center. the ponies simultaneously start walking toward each other across the turntable. as they walk, what happens to the angular speed of the turntable? (a) it increases(b) it decreases(c) it stays constantconsider the ponies-turntable system in this process is the angular momentum of the system conserved? (a) yes(b) no

A

Explanation:

Given

Two ponies are at Extreme end of turntable with mass m

suppose turntable is moving with angular velocity

Moment of inertia of Turntable and two ponies

let say at any time t they are at a distance of r from center such

Moment of inertia at that instant

conserving angular momentum as net Torque is zero

Thus we can say that angular velocity increases as they move towards each other.        

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.