Assertion: collision | /r/HasProperty | head-on
Facets:
Source sentences:
text: Comparing this with the latter equation gives V 1 •V 2 = 0, so they are perpendicular unless V 1 is the zero vector (which occurs if and only if the collision is head-on).
text: This case implies that a train moving at 60 miles/hr which hits a small rock on the track could send that rock forward at 120 miles/hr if the collision were head-on and perfectly elastic.