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Gauge pressure vs Absolute help please?

7. The weight of a car of mass 1.20 × 10^3 kg is supported equally by the four tires,

which are inflated to the same gauge pressure. What gauge pressure in the tires is

required so the area of contact of each tire with the road is 1.00 × 10^2 cm^2? (1 atm = 1.01

× 10^5 Pa.)

A) 11.6 × 10^5 Pa

B) 11.6 × 10^4 Pa

C) 2.94 × 10^5 Pa

D) 2.94 × 10^4 Pa

E) 2.94 × 10^3 Pa

The answer is C according to my professor

Here's my question, isn't that the absolute pressure ? 

Isn't the total pressure exerted by the tires = to gauge pressure+atm ?

By doing Force / 4A 

aren't I getting the total pressure ?

2 Answers

Relevance
  • oubaas
    Lv 7
    1 year ago

    pressure p = m*g*10^4/(4*10^2) = 1.2*10^3*9.806*10^2/4 = 2.94*10^5 Pa answer C)

  • ?
    Lv 7
    1 year ago

    The atmosphere is pushing on the outside of the tires, so the gauge pressure is the net outward pressure that they can exert. Think of it this way: if the absolute pressure in the tires were 1 atm (gauge pressure = 0), they would do absolutely nothing to support a vehicle. As you well experience when you have a "blowout" !

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