J 6

Gasoline tanker truck. When gasoline is loaded onto a tanker truck or dispensed from it into an underground tank at a gasoline station, great care must be taken so that a spark from electrostatic charges does not ignite the vapor. That charge is produced by the sloshing of the gasoline as it moves through hoses or when the truck travels along a road. For gasoline vapor, the critical value for the spark energy is Ucritical = 24 mJ. To avoid fire and explosion, the truck must be grounded before gasoline is poured into it or poured out of it. The grounding is by means of a conducting cable with a resistance of 7.76 0, with one end buried in the ground and the other clipped to the truck (see the figure below). If a truck has a 612 pF capacitance and an initial potential energy of 2.80 J, how much time is required to discharge the truck to the critical value of potential energy? Saferack Number Units