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# The height at which the atmosphere cases to exist is about 80km. If the atmospheric pre...

### Question

The height at which the atmosphere cases 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

(ρm = 13.6g/cm$$^3$$ ρ = 0.00013g/cm$$^3$$ )

### Options

A) 380mmHg

B) 570mmHg

C) 190mmHg

D) 480mmHg

The correct answer is B.

### Explanation:

ρ$$_m$$h$$_m$$ = ρ$$_a$$h$$_a$$
13.68(760 - p) × 10$$^{-3}$$ = 13 × 10$$^{-5}$$(20 × 10$$^3$$)

 760 - p = 13 × 10$$^{-5}$$ × 20 × 10$$^{3}$$ 13.68 × 10$$^{-3}$$ = 19 × 10$$^{1}$$

760 - p = 190
p = 760 - 190 = 570mmHg

## Dicussion (1)

• ρ$$_m$$h$$_m$$ = ρ$$_a$$h$$_a$$
13.68(760 - p) × 10$$^{-3}$$ = 13 × 10$$^{-5}$$(20 × 10$$^3$$)

 760 - p = 13 × 10$$^{-5}$$ × 20 × 10$$^{3}$$ 13.68 × 10$$^{-3}$$ = 19 × 10$$^{1}$$

760 - p = 190
p = 760 - 190 = 570mmHg