The height at which the atmosphere ceases to exist is about 80km. If the atmospheric pressure on the ground level is 760mmHg, the pressure at a height of 20km above the ground level is
A
380mmHg
B
570mmHg
C
190mmHg
D
480mmHg
Verified Correct Answer: B.
Physical Principles & Numerical Solution
(p - 760)/(0 - 760) = (h - 0)/(80 - 0)
∴ (p - 760)/-760 = (20 - 0)/80
80(p-760) = -760(20-0)
∴80p - 60800 = -15200
80p = 60800 - 15200
80p = 45600
∴ p = 45600/80
p = 570mmHg
Source: Myschool Past Questions Archive (Record #1504)