What do you want to starting reactants in an airbag system to have a higher density or lower density? why?

Idon’t understand this page, can someone ?

Three cards with holes are arranged in a straight line. a light is shined through the first card’s hole and travels through all three cards. what does this tell you about light rays? a) that light is reflected b) that light is refractive c) that light travels in a straight line d) that light does not travel in a straight line

Which of these expressions are correct variations of the combined gas law? p1v1t2 = p2v2t1 both