Float That Boat!

Posted by zeerebel on Sep 9, 2011 in Annoucement, Arts, Math, MST, Science |

Have you ever wondered how a ship made of steel can float? In this project you’ll investigate how much weight boat hulls of various shapes and sizes can support without sinking.

You know from experience that if you drop a steel bolt in a bucket of water that it will sink like a rock to the bottom. On the other hand, you know that ships made of steel can float. How does it work?

What determines whether an object floats or sinks? It’s the density (mass per unit volume) of the object compared to the density of the liquid. If the object is more dense than the fluid, it will sink. If the object is less dense than the fluid, it will float. If the object has the same density as the fluid it will neither sink nor float.

With a steel-hulled ship, it is the shape of the ship’s hull that matters. The hull encloses a volume of air, so that the total density, defined as:

(mass of steel hull + mass of enclosed air) / volume,

is less than that of water.

Archimedes discovered that an object immersed in water displaces a volume of water equal to the volume of the object (see Junior Engineering, 1997, for the whole story). The displaced water creates an upward force on the object. If the weight of the displaced water is greater than the weight of the object, the object will float.

In this project you will make some boat hulls of various shapes and sizes using simple materials (like aluminum foil and tape). Can you predict how many pennies each of your boats will support without sinking?

http://www.sciencebuddies.org/science-fair-projects/project_ideas/Aero_p020.shtml

Terminology

buoyancy
The density of an object is one of its most important and easily-measured physical properties. Densities are widely used to identify pure substances and to characterize and estimate the composition of many kinds of mixtures. The purpose of this lesson is to show how densities are defined, measured, and utilized, and to make sure you understand the closely-related concepts of buoyancy and specific gravity. - http://www.chem1.com/acad/webtext/pre/density.html
It is sometimes more convenient to express the volume occupied by a unit mass of a substance. This is just the inverse of the density and is known as the specific volume. - http://www.chem1.com/acad/webtext/pre/density.html
Buoyant Force
Archimedes of Syracuse (Greek: Ἀρχιμήδης; c. 287 BC – c. 212 BC) was a Greek mathematician, physicist, engineer, inventor, and astronomer. Although few details of his life are known, he is regarded as one of the leading scientists in classical antiquity. Among his advances in physics are the foundations of hydrostatics, statics and an explanation of the principle of the lever. He is credited with designing innovative machines, including siege engines and the screw pump that bears his name. Modern experiments have tested claims that Archimedes designed machines capable of lifting attacking ships out of the water and setting ships on fire using an array of mirrors.^[1]
Archimedes is generally considered to be the greatest mathematician of antiquity and one of the greatest of all time.^[2]^[3] He used the method of exhaustion to calculate the area under the arc of a parabola with the summation of an infinite series, and gave a remarkably accurate approximation of pi.^[4] He also defined the spiral bearing his name, formulae for the volumes of surfaces of revolution and an ingenious system for expressing very large numbers.Archimedes died during the Siege of Syracuse when he was killed by a Roman soldier despite orders that he should not be harmed. Cicerodescribes visiting the tomb of Archimedes, which was surmounted by a sphere inscribed within a cylinder. Archimedes had proven that the sphere has two thirds of the volume and surface area of the cylinder (including the bases of the latter), and regarded this as the greatest of his mathematical achievements.Unlike his inventions, the mathematical writings of Archimedes were little known in antiquity. Mathematicians from Alexandria read and quoted him, but the first comprehensive compilation was not made until c. 530 AD by Isidore of Miletus, while commentaries on the works of Archimedes written by Eutocius in the sixth century AD opened them to wider readership for the first time. The relatively few copies of Archimedes’ written work that survived through the Middle Ages were an influential source of ideas for scientists during the Renaissance,^[5] while the discovery in 1906 of previously unknown works by Archimedes in the Archimedes Palimpsest has provided new insights into how he obtained mathematical results.^[6]

http://www.youtube.com/watch?v=6MHX9kecyv8&feature=relatedResources