Force and center of gravity for a steel mud gate

[bcd201115]

Homework Statement

A false mud gate made of common steel for a damn is 6'6" wide, 21'1" tall, and 1/2" thick. Assume a constant density throughout. What is the required force to lift this gate if it were laying flat on the ground and a hoist was attached to the center of gravity? also where is its center of gravity?

Homework Equations

Can anyone help me get started on this at least? It would be great if you could, thanks.

The Attempt at a Solution

 

[PhanthomJay]

Calculate the volume of the steel gate in cubic feet. Steel weighs about 490 lbs/cu ft. The lifting force of the hoist must be equal to the gate's weight in order to lift it slowly off the ground.

 

[bcd201115]

Okay i have the force now, how would i find the center of gravity?