Fluid static problem with wooden block being pulled down

[tonnieee]

Homework Statement

The figure below shows a metal object (2) hanging by a thin cord from a floating wooden block (1). The wood block has a SG of 0.3 and dimensions of 50mm x 50mm x 10mm. The metal part as a volume of 6600m^3. Find the mass of the metal part and the tension in the cord. Work in gage pressure.

Homework Equations

Specific weight = W / m^3
Pressure = specific weight X h = pgh
W = mg

The Attempt at a Solution

I find pressure on the point at the bottom of the wooden block - P = 9810 X 0.01

If I am not wrong, that is the tension in the cord ? But I am totally unsure on how to go about solving the mass of the metal part. I suspect that I need to use specific weight = W / V since they gave volume. But how am I suppose to find the specific weight ? Thanks..[/B]

 

[Doc Al]

I suggest starting by identifying the forces acting on each object. What forces act on the wooden block?

 

[tonnieee]

I suggest starting by identifying the forces acting on each object. What forces act on the wooden block?

Force acting downwards by its weight and the metal block? The force acting upwards by the cord ? But how these are going to affect my calculations hmm

 

[Doc Al]

Force acting downwards by its weight and the metal block?

Three forces act on the wooden block: buoyant force, weight, tension in the cord. What must they add to?

But how these are going to affect my calculations hmm

You calculated the pressure at the bottom of the block. Pressure is not a force, for one. And you neglected the weight of the block.

 

[tonnieee]

Three forces act on the wooden block: buoyant force, weight, tension in the cord. What must they add to?You calculated the pressure at the bottom of the block. Pressure is not a force, for one. And you neglected the weight of the block.

Is there a way to find the forces ? I was not really taught about this in fluid statics.

 

[Chestermiller]

Have you heard of Archimedes principal?

 

[tonnieee]

Have you heard of Archimedes principal?

No

 

[Chestermiller]

No

Well, you need to learn about that before you can solve this problem.

 

[haruspex]

Have you heard of Archimedes principal?

He was the head of the school young Archimedes attended, right?

 

[Chestermiller]

He was the head of the school young Archimedes attended, right?

Ha! Good one.