Editing Elastic collision (section)

====Examples====

;Before collision:
:Ball A: mass = 3 kg,       velocity = 4 m/s
:Ball B: mass = 5 kg,       velocity = 0 m/s
;After collision:
:Ball A: velocity = −1 m/s
:Ball B: velocity = 3 m/s

Another situation:
[[Image:Elastischer stoß3.gif|frame|center|Elastic collision of unequal masses.]]

The following illustrate the case of equal mass, <math>m_A=m_B</math>.

[[Image:Elastischer stoß.gif|frame|center|Elastic collision of equal masses]]

[[Image:Elastischer stoß2.gif|frame|center|Elastic collision of masses in a system with a moving frame of reference]]

In the limiting case where <math>m_{A}</math> is much larger than <math>m_{B}</math>, such as a ping-pong paddle hitting a ping-pong ball or an SUV hitting a trash can, the heavier mass hardly changes velocity, while the lighter mass bounces off, reversing its velocity plus approximately twice that of the heavy one.<ref name=serway258-9>{{harvnb|Serway|Jewett|2014|pp=258–259}}</ref>

In the case of a large <math>v_{A1}</math>, the value of <math>v_{A2}</math> is small if the masses are approximately the same: hitting a much lighter particle does not change the velocity much, hitting a much heavier particle causes the fast particle to bounce back with high speed. This is why a [[neutron moderator]] (a medium which slows down [[fast neutron]]s, thereby turning them into [[thermal neutron]]s capable of sustaining a [[chain reaction]]) is a material full of atoms with light nuclei which do not easily absorb neutrons: the lightest nuclei have about the same mass as a [[neutron]].