Can anyone help me with AP Physics?

Test Preparation
1

<p>I am really stuck on this problem. Ca someone explain it to me?</p>

<p>"A house has a roof with the dimensions shown in the drawing. Determine the magnitude and direction of the net force that the atmosphere applies to the roof when the outside pressure suddenly rises by 10.0mm of mercury, before the pressure in the attic can adjust."</p>

<p>Drawing: <a href="http://img22.imageshack.us/my.php?image=physics8cf.jpg%5B/url%5D"&gt;http://img22.imageshack.us/my.php?image=physics8cf.jpg&lt;/a&gt;&lt;/p>

<p>(Its not very good but basically the length of the top of the roof is 14.5m, the length of the sides of the roof are 4.21m, and the angle that the roof makes with the horizontal is 30 degrees.)</p>

<p>I would really appreciate if anyone could explain this problem to me.</p>

2

<p>Pressure = force / area
So the pressure on the roof is the atmospheric pressure in pascal = N / m^2, the SA of the roof. We just took a test on this today, but it was more ideal gas law based. 1 atm = 760mm Hg = 101325 pascal, when using pascal r=8.3145J/mol K and V = m^3</p>

3

<p>Is the answer 1.7 x 10^5 N ? That seems like too much. Is the area that the force acts on just the surface area of the roof, or does it include the sides of the house that are part of the triangles?</p>