Physics Demo Videos: Fluids

Videos of demonstrations illustrating concepts related to fluids, density, pressure, Archimedes’ Principle, Pascal’s Principle, and Bernoulli’s Principle.

For other videos from our demonstration collection, please visit Physics Demo Videos. You may also wish to view our Video Lecture Series for short tutorials on topics from first year physics.

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Pressure
Bed of Nails. When the pressure is distributed over many nails, each individual nail exerts too small an amount to pop the balloon. When a less dense population of nails is used, each individual nail exerts more pressure and the balloon pops.
Bed of Nails 2: the agony of the feet. When the force is distributed over many nails, each individual nail exerts too small an amount to puncture the foot. Do not try this with only three nails!
Cartesian Diver. The diver-shaped glass in the cylinder has a small hole in the bottom. When pressure is applied to the rubber membrane covering the cylinder, more water is forced into the diver, causing an change in its average density. When this density is less than water, the diver will float; when it is more the diver sinks. Done carefully, an equilibrium point can be found where the diver is suspended in the water.
Crush soda can. A small amount of water is heated in a soda can until steaming. The can is then quickly put in cool water, mouth side down. The sudden change in temp causes the steam to condense, resulting in a significant drop in pressure, making the pressure inside much less than atmospheric pressure. Thus, the can collapses under the pressure.
Magdeburg Hemispheres. Two hemispheres are placed together and evacuated. Pulling even these small hemispheres apart is hard!
Magdeburg Suction Cups. Two suction cups are placed together and compressed to force out all the air. The vacuum seal created when you pull on the suction cups.
Marshmallow Man. The air pockets in jet-puffed marshmallows will expand in a vacuum. This makes the marshmallow man get bigger as the pressure inside the bell jar gets lower.
Shaving Cream in Vacuum. The air pockets in shaving cream will expand in a vacuum. This makes the cream get bigger as the pressure inside the bell jar gets lower.
Which Will Float, Regular or Diet? Sugar is a lot more dense than artificial sweeteners. Thus, a regular soda is more dense than a diet soda. When placed in water, the regular soda, being more dense than water, will sink. The diet, being less dense than water, will float.
Inverted Liquid. An index card is placed on top cylinder full of water. The cylinder is then inverted. A slight vacuum is created, keeping the index card sealed to the cylinder, thus keeping the water from pouring out.
Archimedes’ Principle
Hollow Globe in Vacuum. When in the atmosphere, the globe experiences a buoyancy force upward exerted by air. When the air is removed, the buoyancy force is also removed and it is clear that the globe weighs more than the cylinder.
Pascal’s Principle
Pascal’s Vases. Water pressure is dependent on depth only. Thus, two differently shaped vases will show the same pressure at the same depth.
Bernoulli’s Principle
Bernoulli Envelope. Blowing air over the open end of an envelope causes the two sides to separate due to the lower pressure of the air flowing along the outside of the envelope.
Flettner Rotor. A moving, spinning spool will curve due to the addition or subtraction of pressure effects. The side that is spinning in the direction of the motion will have a higher pressure than the side spinning away, thus the spool will curve to the low pressure side.
Floating Ping Pong Ball. A ping pong ball can be “floated” on a stream of air. The air rushing around the ball creates a pressure low enough to lift and support the ball. The air moves fastest in the center of the stream, so the ball stays centered, even with the nozzle tilted.
Air Over Paper. A stream of air over paper creates a low pressure zone which lifts the paper.
Ping Pong Ball w/Funnel. When a ping pong ball is placed in a funnel with the air blowing out, the ball won’t fall out of the funnel. The rushing air creates an area of low pressure that holds the ball in place.
Boomerang (outside). A boomerang will lift and curve when thrown.
Boomerang (inside). A boomerang will lift and curve when thrown.
Curve Ball. A moving, spinning ball will curve due to the differing pressures on opposite sides of the ball. The side that is spinning in the direction of the motion will have a higher pressure than the side spinning away, thus the ball will curve to the low pressure side.
Siphon. An initial vacuum (provided by sucking) is enough to begin a flow of liquid from the high beaker to the low one.
Venturi Tubes. Air flowing through a narrow pipe created a lower pressure than air flowing through a wider pipe.