# Homework Help: Water manometer to measure change in pressure

1. Oct 28, 2007

### BlueSkyy

1. The problem statement, all variables and given/known data

An experiment to determine the specific heat of a gas makes use of a water manometer attached to a flask (the figure below ). Initially the two columns of water are even. Atmospheric pressure is 1.4 x 10^5 Pa. After heating the gas, the water levels change to those shown. Find the change in pressure of the gas in Pa.

https://chip.physics.purdue.edu/protected/GiambattistaMimg/chapter-09/fig-035.gif

2. Relevant equations

P = pgd (gauge pressure)
Pgauge = Pabs - Patm

3. The attempt at a solution

well, i took (1000 kg/m3)x(9.81m/s2)x(.04m) and got 392.4 kPa...that's 392400 Pa, right?
but it's not correct...where did i go wrong? i know that it is displaced .02m up and .02m down for a total of .04m, and the density of water is 1000kg/m3 (for this problem)

any help would be appreciated!

2. Oct 29, 2007

### rl.bhat

1000x9.81x.04 = 392.1Pa., not kPa