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## Homework Statement:

- Tension in air, water and submerged

## Relevant Equations:

- Archimedes Principle

Hello,

Looking for help on the following:

A crane is used to lower a vertical cylindrical pillar into a reservoir. The pillar has a mass of 4 tonnes and is submerged to a depth of 2.5m. It has a diameter of 1.1m.

The specific gravity of fresh water is 1125kg/m^3, and 9.81m/s^2.

Use a free body diagram to show the forces acting on the pillar when submerged and calculate the upthrust, the tension in the rope in air and the tension in the cable when submerged.

I have this for Upthrust:

Fbuoy = Pbottom x A - Ptop x A

= Delta x P x A

= Pf x g x h x A

= 1.125 x 9.81 x 2.375 = 26.2N

Upthrust = 26.2N

Is this correct?

For the tension on the rope i am really stuck so could do with some help please.

I have that Tension = m x g

4 tonns = 4000kg

4000 x 9.81 = 39,240N

T = 39,240N

I know T = w - Fb

But Fb needs a volume. Which i can't work out because i don't have the height.

But now everything i look to learn so i can complete is says i need the height of the pillar. Can anyone help me please?

Thanks.

Looking for help on the following:

A crane is used to lower a vertical cylindrical pillar into a reservoir. The pillar has a mass of 4 tonnes and is submerged to a depth of 2.5m. It has a diameter of 1.1m.

The specific gravity of fresh water is 1125kg/m^3, and 9.81m/s^2.

Use a free body diagram to show the forces acting on the pillar when submerged and calculate the upthrust, the tension in the rope in air and the tension in the cable when submerged.

I have this for Upthrust:

Fbuoy = Pbottom x A - Ptop x A

= Delta x P x A

= Pf x g x h x A

= 1.125 x 9.81 x 2.375 = 26.2N

Upthrust = 26.2N

Is this correct?

For the tension on the rope i am really stuck so could do with some help please.

I have that Tension = m x g

4 tonns = 4000kg

4000 x 9.81 = 39,240N

T = 39,240N

I know T = w - Fb

But Fb needs a volume. Which i can't work out because i don't have the height.

But now everything i look to learn so i can complete is says i need the height of the pillar. Can anyone help me please?

Thanks.