Find the Mass of Air in the Room and the Air's Weight

  • #1
249
1

Homework Statement



The air in a room measuring 8 ft x 9 ft x 12 ft is at 80°F and 1 atm. Determine the mass of the air, in lb, and its weight, in lbf, if g = 32.0 ft/s2

Homework Equations


1 °F = 460.86°R

dair = mair/vair


The Attempt at a Solution



The air has the same mass as the room, thus mair = 8x9x12

mair = 864 ft3

dair = mair/vair

dair = ρ/RT

dair = 1 atm/(53.35 ft lb/lbm °R)(540.67°R)

dair = 3.4668x10-5 atm lbm/ft lbf

My density seems kinda low. What am I missing? Is it the gc?
 

Answers and Replies

  • #2
SteamKing
Staff Emeritus
Science Advisor
Homework Helper
12,796
1,668
You should check your units, especially for R.

A density unit of atm lbm/ ft-lbf makes no sense.
 
  • #3
249
1
Wrong question.
 
Last edited:

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