Calculating Force Needed to Lift Lid in Denver

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To calculate the force needed to lift a lid on a box evacuated to an internal pressure of 90,000 Pa while the external atmospheric pressure in Denver is 67,500 Pa, one must consider the pressure difference. The calculations initially presented were incorrect due to a misunderstanding of the pressure values. The correct pressure difference leads to a force of 378 N required to lift the lid. The discussion highlights the importance of accurately interpreting pressure values and understanding the implications of external pressure being lower than internal pressure. Proper calculations are essential for determining the force needed in such scenarios.
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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
 
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lalahelp said:

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?
 
the pressure value is 90000 pa
 
lalahelp said:
the pressure value is 67500 pa

9.0 104 Pa is 67500 pa ?

Is it supposed to be 9.0x104 Pa ?
 
Yeh I messed up my bad sorry
 
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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