An aircraft travelling at 600 km/h accelerates steadily
at 10km/h per second. taking the speed of sound as
1100 km/h at the aircraft's altitude, how long will it take to
reach the 'sound barrier'?

50.14 s

Explanation:

We can solve this problem by the following equation:

(1)

Where:

is the final velocity of the aircraft.

is the initial velocity of the aircraft

is the acceleration of the aircraft (taking into account 10 km/h=2.77 m/s and acceleration is \frac{2.77 m/s}{1 s})

is the time it takes to the aircraft to reach the sound barrier

Isolating from (1):

(2)

(3)

Finally:

(4)

nah.   i'm just sleepy.

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.