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Engineering College Question!!! View All
Very stuck at the moment. Any help appriciated........

A block of concrete measuring 1.25m x 1.5m x 250mm is required to be lifted from the sea bed to the surface. To assist the divers, inflatable lifting bags will be used.

Calculate how many kilograms the bags will have to be able to lift?

Take the density of concrete as 2403kg/m^3 and sea water as 1030kg/m^3

Thanks in advance

7 years ago - 3 months left to answer. - 1 response - Report Abuse
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This is a buoyancy problem. I will not give you the answer, but I will provide you with some guidance to help you find the answer. I will provide you with some reference links which have pictures which should help.

Currently the block has a negative buoyancy based on the volume of the block times the difference in the density of the block and the water. [1]

What is that difference?

What is the volume of the block?

What is the difference in density between the block and the water?

How many cubic meters of water is required to equal that difference?

For the sake of the calculation assume that the air is a perfect displacer and you have displace 1030kg/m^3 for every cubic meter of airbag. This will tell you how big that air bag must be.

As you explore this problem further you can determine how much total air you will need to inflate that airbag to the required volume.

If you have more questions do not hesitate to ask. I will try to give you some guidance to help you learn.

Niel Leon

7 years ago

Source: [1]

  0     0  does not provide engineering advice. The Ask@ service is a forum for members to exchange ideas relating to the world of engineering. We caution users not to accept any responses that they receive without further validation, and not to rely on any engineering advice that they may get from other members of the Ask@ forum. specifically disclaims any obligation to validate or verify any information posted within the Ask@ service. encourages users to seek the services of a professional engineer for any engineering advice they may require.