# Homework Help: Hydrostatics- need volume of submerged block- confused

1. Oct 19, 2009

### jonquest

hydrostatics- bouyancy-need volume of submerged block- confused

1. The problem statement, all variables and given/known data

Need help with #11 attached

tank has 2m of water
gate is 1 m wide
pulley is 1/2 m above water
specific weight of concrete is 23.6 kN/m3
need to find voulme of water to keep gate closed

2. Relevant equations

Bouyant force= volume x specific weight
Force= specific weight x area x centroid height

3. The attempt at a solution

Force on gate is: Force= specific weight x area x centroid height 9810 N/M x 1m2 x 1/2 m
force on gate + Bouyant force + weight of concrete= 0

I've got:
(9810 N/M x 1m2 x 1/2 m) - (23.6 kN/m3 x volume)+ weight of concrete=0

not sure where to get weight of concrete? do I count the weigh of the water above? does the height of the pully have to be considered?

#### Attached Files:

• ###### FMAssignment5.pdf
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Last edited: Oct 20, 2009