Puzzled physics teacher alert!
A problem in our text asks to solve for the mass of a car and provides you with the area of contact of the tires with the road and the GAUGE pressure in the tires. The intent is for you to use the product of Pressure and the total Area to solve for a force (weight) from which you can determine the mass of the car.
I solved for the Absolute Pressure (including atmospheric pressure) before plugging it in to solve for force. However, the solution in the text shows them only using the gauge pressure to solve for the force & mass.
Why would we use the gauge pressure instead of the absolute (true) pressure in this problem?