Airbag Investigation

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Airbags are “automotive passive restraints consisting of a bag that is designed to inflate upon collision and prevent passengers from pitching forward”. (Answers Corporation, 2010) They are inflated from the reaction of sodium azide (NaN3) and potassium nitrate (KNO3), which produce hot nitrogen gas; this is the equivalent explosive force of a rocket booster. (HowStuffWorks Inc, 2010) The action of inflation occurs within 45-55 milliseconds. Deflation occurs through holes in the bag. The whole process of inflation and deflation occurs within 75-80 milliseconds. (SafetyForum, 2010) Newton’s first law of motion is Inertia; that an object will continue to move with constant velocity unless acted upon by an external resultant force. This means that a car in motion will keep travelling forward unless an external force (e.g. a brick wall) is applied. Hence without an airbag, the person will continue travelling forward; the momentum of the person to falling forward against the steering wheel will kill him. The airbag will inflate when a collision force equal to running into a brick wall at 16 to 24 k/h. (HowStuffWorks Inc, 2010) The second law is that force is proportional to mass and acceleration. This means that if a greater force is applied on an object, there will be a greater acceleration; a heavy object would require more force to move. This is related to airbags through the equation: F=ma

a=(v-u)/t
u=0
∴a=v/t
∴F=mv/t
According to the above equation, time affects the force; the longer the time, the less the force. An airbag increases the time of impact, therefore decreasing the force which a person feels upon impact. This experiment will investigate airbag inflation, substituting sodium azide and potassium nitrate for sodium bicarbonate/baking soda (NaHCO3) and vinegar/acetate acid (CH3COOH); these substances will produce a chemical reaction: NaHCO3 (aq) + CH3COOH (aq)  CO2 (g) + H2O (l) + CH3COONa (aq)

Sodium Bicarbonate + Acetate Acid  Carbon dioxide + Water + Sodium Acetate The ratio of sodium bicarbonate/baking soda (NaHCO3) and vinegar/acetate acid (CH3COOH) will be experimented upon to produce the fastest inflation. The experiment will be conducted within a plastic bottle with a balloon attached firmly on top. The two substances react to produce carbon dioxide; the balloon will collect this gas, inflating in the process. This process replicates nitrogen gas which is produced in an airbag. The dependent variable in this experiment is the time taken for the balloon to inflate fully and the height of the balloon after inflation; the independent variable is the ratio of bicarbonate soda to vinegar. The control variables are the speed at which the two substances were mixed, the size of the balloon and the capacity of the plastic bottle. To create a fair test, measuring cylinders and scales will be used to measure out quantities. The same people will do the same jobs to reduce human error. A new balloon will be used for each test to ensure no bicarbonate soda is already inside the balloon, adding to the quantity.

Aim
To replicate airbag inflation by experimenting with balloons, bicarbonate soda and vinegar and find the ratio which inflates the balloon the fastest.

Risk Management
ActivityRiskManagement
Handling chemicals Eye irritation; smarting and reddening of the eyeWear safety goggles, do not rub eyes Using glassware such as measuring cylinders, beakers, etc.Dropping on the floor and sharps breaking, cutting peopleHandle glass equipment with caution; wear covered shoes. Use dustpan to pick up sharps to avoid injury and dispose in the sharps bin. Inhalation of vapoursIrritation to the respiratory tractAvoid sniffing or putting the fact too close to powdered substances.

MSDS
Bicarbonate soda
Inhalation:
High concentrations of dust may cause coughing and sneezing. Ingestion:
Extremely large oral doses may cause gastrointestinal disturbances. Skin Contact:...
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