Susan pushes her dad, David, on an ice rink with a force of 30 N. She weighs 45 kg and her dad weighs 100 kg. What are the accelerations of Susan and David?

a(Susan) = 0.67 m/s², a(dad) = 0.3 m/s²

Explanation:

Assuming no other forces acting on both bodies in the horizontal direction (neglecting friction due to they are standing on ice), the interactions between them must obey Newton's 3rd law, so the magnitude of the force exerted by Susan on her dad (30N) must be equal to the one exerted by her dad on her.

So we can find the accelerations, just applying to their masses Newton's 2nd Law, as follows:

Fs = ms*as = 30 N

⇒ as =

Fd = md*ad = 30 N

frequency or wavelenth of em radiation in a vacuum

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.