The gauge pressure in each of the four tires of an automobile is 230 kpa. if each tire has a "footprint" of 180 cm2 (area touching the ground), determine the mass of the car.

Since there are four tires, the total area is 0.018m^2 * 4 = 0.072m^2. Pressure = force / Area = > 180*10^3 = Force/0.072 = > Force = 12960 N. Then we plug the result for Force into Force = Mass * Acceleration = > 12960 = mass*9.8m/s^2 = > Mass = 1322.4kg. (Note that 9.8m/s^2 is the gravitational constant for acceleration.)