Abullet of mass m1 = 5 g is moving with speed v1. it strikes a block of mass m2 = 6 kg that is hanging at rest from a cord. the bullet embeds itself into the block and the bullet and block swing up on the cord, coming to rest at a height h = 2 cm above the original position of the block. what is the correct expression for momentum conservation when the bullet strikes the block?

The initial velocity of bullet is 7518.26 m/s.

Explanation:

Given that,

Mass of bullet = 5 g

Mass of block = 6 kg

Height = 2 cm

We need to calculate the velocity

Using conservation of energy

We need to calculate the velocity of bullet

Using conservation of momentum

Put the value into the formula

Hence, The initial velocity of bullet is 7518.26 m/s.

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.