A friend asks you how much pressure is in your car tires. You know that the tire
ID: 2187622 • Letter: A
Question
A friend asks you how much pressure is in your car tires. You know that the tire manufacturer recommends 30 { m 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 { m kg}. It seems reasonable to assume that each tire supports one-fourth of the weight. With the ruler you find that the tires are 15 { m cm} wide and the flattened segment of the tire in contact with the road is 13 { m cm} long.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