# Pressure

#### BestDoctorEver

##### Membership Revoked
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5+ Year Member
A gas is trapped in an inverted test tube suspended within a beaker of water. If the water level in the test tube is 1 cm higher than the water level in the beaker, then the pressure of the trapped gas is most nearly equal to:
A. 0.76 atm.
B. 0.82 atm.
C. 0.86 atm.
D. 1.0 atm.

#### MrNeuro

##### Full Member
7+ Year Member
A gas is trapped in an inverted test tube suspended within a beaker of water. If the water level in the test tube is 1 cm higher than the water level in the beaker, then the pressure of the trapped gas is most nearly equal to:
A. 0.76 atm.
B. 0.82 atm.
C. 0.86 atm.
D. 1.0 atm.

dp = rho water*g*dh

change in pressure = 1000 kg/m^3*10 m/s^2*0.01 m

1 x 10^2 Pa = 1x10^-3 atm
1- 1x10^-3 atm = ~1 atm

#### dmf2682

##### Membership Revoked
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Sometimes in engineering they still use inches of water as units for pressure, indicating the height of a water column under a given pressure differential. An inch of water is approximately 1/27 psi which in turn is 1/14.7 atm. So a centimeter of water is a very small amount of pressure difference from atmospheric.

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