Hippos spend much of their lives in water, but amazingly, they don’t swim. manatees, they have, like little very body fat. the density of a hippo’s body is approxi-mately 1030 kg/m3, so it sinks to the bottom of the freshwater lakes and rivers it frequents—and then it simply walks on the bottom. a 1500 kg hippo is completely submerged, standing on the bottom of a lake. what is the approximate value of the upward normal force on the hippo?

428.59 N

Explanation:

Buoyant force, where V is volume, g is gravitational constant and \rho is density

where is upward force

where is the density of hippo

Using g as 9.81

Therefore, the upward force=428.59 N

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.