A friend asks you how much pressure is in your car tires. You know that the tire
ID: 2029301 • Letter: A
Question
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 do find the owner's manual and a ruler. Fortunately, you've just finished taking physics, 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. With the ruler you find that the tires are 18 cm wide and the flattened segment of the tire in contact with the road is 12 cm long.What answer will you give your friend?
Explanation / Answer
wt of car = 1500 * 9.8 = 14700 N
area of contact of 1 tyre = 15*13 cm2 = 195 cm2
total area of contact for 4 tires = 780 cm2 = 0.078 m2
Pressure in pascaks = 14700/0.078 = 188461.538 Pa
1 Pascal = 0.00014503773800 Psi
=> 188461.538 Pa = 27.33 psi (ans) which is lower than the recommended 30psi