Physics of Buoyancy

Question 1

What is the definition of buoyancy?

Answer 1

The tendency or capacity to remain afloat in a liquid. That statement is based on something first discovered by the ancient Greek scientist Archimedes, who lived over 2200 years ago.

Question 2

What force does buoyancy provide on an object?

Answer 2

Buoyancy provides an upward force on an object. The magnitude of this force is equal to the weight of the displaced fluid.

Question 3

What relationship does volume have to buoyancy?

Answer 3

Buoyancy depends on volume and so an object’s buoyancy reduces if it is compressed and increases if it expands. For example, a wetsuit will be compressed as depth increases and thus the volume of the suit will reduce and so will the buoyancy.

Question 4

What is positive buoyancy?

Answer 4

Positive buoyancy is when the object displaces more water than it weighs. The buoyancy is expressed as a positive number, such as being “2 kilograms/4.4 pounds positive.” Generally this would mean the object is floating on the surface and could hold a further 2 kg/4.4 lb of weight before it starts to sink.

Question 5

What is neutral buoyancy?

Answer 5

Neutral buoyancy is when the object that weighs exactly the same as the water it displaces neither floats nor sinks. Adding or removing weight will make it sink or float. The diver’s goal whilst most of the time underwater is to neither sink nor float.

Question 6

What is negative buoyancy?

Answer 6

Negative buoyancy is when the object sinks. The weight of the object is more than the water displaced by it. Negative buoyancy is expressed as a negative number, such as “2 kilograms/4.4 pounds negative.”

Question 7

What does 1 litre of sea water weigh?

Answer 7

1 litre of sea water weighs 1.03 kg.

Question 8

What does 1 litre of fresh water weigh?

Answer 8

1 litre of fresh water weighs 1 kg.