At dawn and dusk, large amount of blue and violet light(shorter wavelength) has been scattered so, the light that is recieved by an observer is mostly of a longer wavelength and therefore appears to be red.
Water is a vital substance for life on Earth, and it plays numerous important biological roles in living organisms. Some of the key biological roles of water are:
Universal solvent: Water is an excellent solvent for many substances, both organic and inorganic. This means that it can dissolve and transport a wide range of nutrients and minerals necessary for the growth and survival of living organisms.
Medium for metabolic reactions: Many metabolic reactions in living organisms require water...
Yes, if the angle between the two vectors is more than 90o but less than 2700. (cosΘ is negative)
The two vectors (say A and B) of different magnitudes cannot be combined to give zero resultant since minimum value of combination is ІA-BІ which is not zero if AB.
The three vectors A, B and C of different magnitudes can be zero such that they form a closed triangle, then,
A+B+C=0
or, C=-(A+B)
Hence, the sum of three vectors may be zero if vector sum of any two vectors is equal and opposite to the third vector.
Note: The vectors can give this result only if...

Materials show varying behaviors based on their Poisson's ratio. High Poisson's ratio materials (near 0.5) contract significantly sideways when stretched and expand when compressed, seen in substances like rubber. Low Poisson's ratio materials (near 0) undergo minimal width change during axial deformation, typical of metals and common engineering materials.