Assertion (A) : The safety air bags fitted in some cars inflate during head-on impact of the car. Reason (R) : The inflation is due to pumping of air into the balloon during the impact.

Assertion (A) is true as safety airbags are designed to inflate during a head-on impact to provide a cushion for passengers. However, Reason (R) is false because the inflation is not caused by pumping ambient air into the balloon. Instead, it is the result of a rapid chemical reaction [1]. When sensors detect a significant collision, they trigger an electrical signal that ignites a chemical propellant, typically sodium azide (NaN3). This compound undergoes extremely rapid thermal decomposition to produce nitrogen gas (N2) and sodium metal. The nitrogen gas fills the airbag in approximately 15 to 50 milliseconds, providing the necessary cushioning effect. Modern systems may use alternative gas generators, but the mechanism remains a chemical reaction rather than mechanical air pumping.

Sources

1. [1] https://www.scientificamerican.com/article/how-do-air-bags-work/