$Q(10)$ Figure Q $10$ shows a sluice gate that is designed to open by rotating about A $.$

The hinge A is $2\mathrm{.}5$ m above B and the gate is $2$ m wide $($depth into the page$).$ What

magnitude should the mass located $1$ m to the right of A have if the gate is designed

to open when the water level h reaches $1\mathrm{.}5$ m above B $.$ You may ignore the mass or

the gate. $($Density of water, $=1000k\frac{g}{m^3}.)$