Posted by Elisa on .
drwls for the question below, the answer seems to be wrong:
The four tires of an automobile are inflated to a gauge pressure of 1.8 multiplied by 105 Pa. Each tire has an area of 0.025 m2 in contact with the ground. Determine the weight of the automobile.
It asks for the answer in N and I get 2.8E4 N

physics: drwls 
drwls,
That is the answer I came up with yesterday. As I said before, they may want you to multiply contact area by gauge pressure instead of absolute pressure, as I did. I don't agree with that method. If you do it that way, you get 1.8^10^4 N for the car's weight.
I cannot be of any further assistance on this question. Approximations have to be made to come up with an answer. There are additional forces within the portion of the tire that makes contact, that end up being ignored.