Physics Help Forum statics problem, help needed

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 May 11th 2019, 12:00 AM #1 Junior Member   Join Date: May 2019 Posts: 5 statics problem, help needed Hello Problem description: determine the lenght of h with respect to b so that the water flows. ive gotten as far as come up with an equation for the sum of moments and it goes as follows: $\displaystyle bh*1/2b-1/2hb*1/3b=0$ the answer is wrong and i dont know why. moment arm on the b is 1/2b and the moment arm on h is 1/3h because of the way water pressure works , meaning its a uniform load in the shape od triangle. the answer to this problem is supposed to be $\displaystyle sqrt3 *b$. Any help appreciated. Attached Thumbnails
 May 11th 2019, 02:28 AM #2 Senior Member   Join Date: Apr 2017 Posts: 476 force acting on face length b .....= dencity x b x width x gravity x h , this acts at center of face so the turning torque is... dencity x 1/2 x b x b x width x gravity x h Force acting on face h is ....= 1/2 dencity x h x width x gravity x h This force acts 1/3 of the way up (www.youtube.com/watch?v=WkM1tCZDM2c) so torque is ..... = 1/3 h x 1/2 dencity x h x width x gravity x h tipping occurs when two torques are equal so b x b = 1/3 x h x h so 3 b squared = h squared .... h = root 3 b topsquark and dbag like this.
 May 11th 2019, 03:14 AM #3 Junior Member   Join Date: May 2019 Posts: 5 thank you very much

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