Air pressure

  • Thread starter lalahelp
  • Start date
  • #1
75
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Homework Statement


A lid is put on a box that is 14 cm long, 12 cm wide, and 8.0 cm tall and the box is then evacuated until its inner pressure is 9.0 104 Pa.

How much force is required to lift the lid in Denver on a day when the atmospheric pressure is 67.5 kPa (2/3 the value at sea level)?


The Attempt at a Solution



(67500-90000)*.o168
=-378 N

I Keep getting my answer wrong could someone help please
 

Answers and Replies

  • #2
gneill
Mentor
20,913
2,862

Homework Statement


A lid is put on a box that is 14 cm long, 12 cm wide, and 8.0 cm tall and the box is then evacuated until its inner pressure is 9.0 104 Pa.
Can you clarify that pressure value?
 
  • #3
75
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the pressure value is 90000 pa
 
  • #4
gneill
Mentor
20,913
2,862
the pressure value is 67500 pa
9.0 104 Pa is 67500 pa ???

Is it supposed to be 9.0x104 Pa ?
 
  • #5
75
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Yeh I messed up my bad sorry
 
  • #6
gneill
Mentor
20,913
2,862
Okay, then your working seems fine. What does it mean if the pressure outside is now less than what the pressure in the box is (or was!).
 

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