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physocs1

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## Homework Statement

The rectangular gate shown in section is 3 m long (perpendicular to the paper) and is hinged about its upper edge B. The gate divides a channel leading to a fresh-water lake on the left and a salt-water tidal basin on the right. Calculate the moment, M, on the shaft of the gate at H required to prevent the gate from opening when the salt-water level drops to h = 1 m. Take the density of salt water 1050 kg/m3

## Homework Equations

1. Force=rho*g*v

2. F=gamma*h*a

3.R= rho*g*h*a

Where gamma = specific weight of liquid

Where R=hydrostatic pressure

## The Attempt at a Solution

Calculate Both forces acting on rectangle gate. Then solve for the moment

Using sum of moments

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I am confused on which equation to use. I want to use 3. since its a flat surface but I confused whether to use gravity in the equation?

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