The bulk modulus of water is about 2.2 x 109 Pa, which means that a change of 1 N/m2 of external pressure on the liquid is able to change a given volume of it by a factor of 4.5 x 10-10 (for comparison, the same pressure change would produce a volume change of about 7 x 10-6 for air and 7 x 10-12 for cast steel ). So if we can completely fill a Florence flask with water, we can use it as a hammer to drive a nail into a board!
We have three 20 oz. soda bottles, one filled with water, one filled with sand, and one filled with air. A spring scale shows the water-filled bottle to weigh approximately 6N in air, and nearly 0N when it is fully submerged in a large container of water. Since gravity is still acting on the bottle when it is submerged in the water, there must be a force of 6N pushing up on it. This is the buoyant force.
We can do the same experiment with the bottle of sand. This bottle weighs roughly 13N in air, but when it is fully submerged in water it weighs 6N less. Even...
Bernoulli's Principle states that the pressure exerted by a fluid is velocity dependent; the faster the velocity the lower the pressure. This can be demonstrated by a form of Venturi tube, a pipe with a narrow constriction which forces an increase in fluid velocity.
How it works
The varying cross-section of the wind tunnel forces air to travel its length at different velocities, with the highest velocity being at its most constricted part. From equipartition of energy, the increased energy in one degree of freedom (the kinetic energy of the flow)...
For a body to reach terminal velocity when falling through a fluid, the drag force (given by Stoke's Law) coupled with the buoyant force (from Archimedes' principle) need to balance the falling object's weight. Leaving derivations to other great texts you end up with
Poiseulle determined that the laminar flow rate of an incompressible fluid along a pipe is proportional to the fourth power of the pipe's radius. To test his idea, we'll show that you need sixteen tubes to pass as much water as one tube twice their diameter.
How it works
Poiseulle's law states that the flow rate Q is also dependant upon fluid viscosity η, pipe length L, and the pressure difference between the ends P by
Bread dough is stiff but still flows. A big blob of foodstuff that slumps over time, like Silly Putty but large and edible.
Make bread dough enough for a couple loaves, and knead it stiff enough that a round ball of dough takes half an hour to slump to half its original height. Place on a plate, put a camera on it. Project the image at the beginning, just as the dough ball is released, and again some time later, after viscous flow.
An egg size piece of clear ice is dropped into a hot frying pan, with hissing and melting and steaming from solid to liquid to gas . An egg is carefully dropped into another hot frying pan, and it transforms from liquid to solid.
A small water bottle in the freezer overnight will freeze solid. Cutting off the plastic and breaking the ice with a hammer will generate the egg size piece of ice.
A brownie pan with two food safe thermocouples, one in the brownie batter and one in the air next to the pan, is put in a pre-heated oven, and the temperature profiles recorded and displayed.
Clean copper wire is used to make an armature for the thermcouple wires. Crimp the center of a 20 cm piece of 14 ga wire on the side of the baking pan. Bend loops at the ends of the copper wire to hold the thermocouple wire.
The oven temperature thermocouple should be about five centimeters away from the pan, at the same level as the center of the pan. The brownie thermocouple is...
A volunteer puts her hands in oil and water in large beakers on thermostated hot plates, at about 60°C. The water beaker hand is removed almost instantly. The oil beaker hand can remain indefinitely.
The heat capacity of oil is about half that of water. Oil is thought of as hotter because it can be heated to higher temperatures than boiling water, but at the same temperature, water moves more heat into your hand than oil does.
Vinegar and two different amounts of baking soda in plastic soda bottles with balloons.
Two 500ml PETN soda bottles of the same make, split a bottle of vinegar between them.
11" balloons are pre-inflated with dry air, with care taken not to stretch the neck of the balloon. Into the balloons with a funnel go one, two teaspoons of baking soday. With 250 ml of vinegar, that's like six liters of gas potential if one carbon dioxide comes from one acid hydrogen ion.
Tap the baking soda powder down away from the neck of the balloon. Stretch the neck and place it over the top...
Simulation of the greenhouse effect with silvered and unsilvered glass bottles.
What it shows:
Heat energy readily escapes from a clear glass flask, but is trapped inside a silvered flask which rapidly heats up.
How it works:
Two 2L flat bottom Florence flasks, one clear and one silvered (see reference), have identical 10Ω, 25W resistors placed inside them connected in series to a DC supply 1 These resistors act as good sources of infrared radiation. The clear flask readily transmits the IR, but the silvered...
OHP representation of lines of force using bar magnet and iron filings.
What it shows:
The magnetic field lines of the Earth can be represented by the field lines of a bar magnet.
How it works:
The Earth's magnetic field is basically a magnetic dipole. It can therefore be represented to first approximation by the field of a bar magnet. The shape of the field lines can be highlighted by the sprinkling of iron filings, or by the use of plotting compasses. The latter method has the advantage of showing the variation of dip...
As shown in the drawing, the Mercator projection is a cylindrical map projection of the spherical globe. The meridians and parallels of latitude on the globe end up appearing as lines crossing at right angles in the projection. Areas on the globe far from the equator appear to be much larger on the projection. It's not trivial to visualize this projection and the intention of this demonstration is to shed some light on it (literally).