Why is red colour used as a sign of danger?

Red light is used as a sign of danger because it has the the least deviation and longest wavelength that allows it to be clearly visible at night and hence causing less accidents.

grav forces affect all objects magnetic forces affect magnetic objects and electric currents

firearm identification is the process of analyzing the bullets and cartridge cases left at a crime scene to determine if they came from a particular firearm. marks on the bullets and cartridges may be common to every firearm of that type. these are called class characteristics.