The angle a vector makes with the x-axis of a coordinate system must be what size in order to make one or more of its components negative? less than 30 degrees between 30 and 60 degrees between 61 and 90 degrees greater than 90 degrees

It should be greater than 90°.

The components of a vector of magnitude 'V' making angle θ with the x-axis are given by,

Horizontal/x component = VCosθ

Vertical/y component = VSinθ

For for any value of θ≥90°, either of or both the component is negative.

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.

conservation of mass

mass before something happens = mass afterwards