Some clover plants produce cyanide to deter herbivores, but…

Some clover plants produce cyanide to deter herbivores, but the allele for cyanide production makes them more likely to be killed by frost. In warmer southern regions clover populations have a high proportion of cyanide producing alleles, but in colder northern regions, the proportion of cyanide producing alleles is very low. These genetic differences between northern and southern populations is known as:

Why do passengers in an automobile get whiplash in a sudden…

Why do passengers in an automobile get whiplash in a sudden stop or rear impact collision?  Why do airbags help to reduce whiplash? Make sure you explain using the Laws/Theories/Principles of Physics.  {For the airbags, there are three different ideas/laws/theories/principles which can apply. You only need to choose one of them.}