Randall D. Knight — Fluids and Elasticity: Problem Problem_42

A friend asks you how much pressure is in your car tires. You know that the tire manufacturer recommends 30 psi, but it’s been a while since you’ve checked. You can’t find a tire gauge in the car, but you just finished taking physics and so you tell your friend, “I don’t know, but I can figure it out.” From the owner’s manual you find that the car’s mass is 1500 kg. It seems reasonable to assume that each tire supports one-fourth of the weight. Using a ruler, you find that the tires are 15 cm wide and the flattened bottom segment of the tire is 13 cm long. Your observation of the tire tread pattern suggests that two-thirds of this segment is in actual contact with the road. What answer—in psi—will you give your friend?