MORE PHYSICS DEMOS
Here are some physics demonstrations that you might like to add to
your "bag of tricks". If you wish to print out a hard copy of these
demos, save it as a "text" file and then import it into your favorite
word processor for formatting and printing.
If you have any of your own that you would like to contribute,
I'll be happy to give you credit and add yours to this list.
Herb Gottlieb from New York City
(where political demonstrations out number physics demonstrations)
[posted with permission]
ADIABATIC HEATING. A
considerable temperature increase occurs when a rubber band is
stretched. Hold a thick rubber band against your upper lip and extend
it quickly. Your lip can sense the increase in temperature. Allow the
rubber band to contract rapidly and note that it suddenly becomes
AIR GLUE. To demonstrate
Bernoulli's principle, cut a circular piece of cardboard slightly
larger than the end of a thread spool. Push a straight pin all the
way into the center of the cardboard. hold the spool so its hole is
vertical. Press the cardboard against the bottom of the spool with
the free end of the pin inside the bottom of the spool hole. Blow
into the top of the spool hole. The air acts like glue and the
cardboard clings tightly to the spool as long as there is air motion
through the spool.
AIR PRESSURE SUCKER. Is
so-called suction a push or a pull? Arrange a flask fitted with a two
hole stopper and a glass tube extending well down into the flask
which is completely filled with water. Challenge a good-natured
student to "suck" water up the glass tube while the instructor holds
a finger over the other hole of the stopper. When the student fails
to get any water out of the flask, instructor might remark, "Jim is
not as big a sucker as we thought." After appropriate comments and
removing the finger from the stopper hole, the instructor asks the
boy to try again. Suddenly the sucker succeeds. When the class
becomes orderly again, explain how air pressure provides the
AIR PUCK. Cut a six inch
circle of plywood or press board. Cement a small cork at its center,
Drill a very fine hole through the disc and cork. Inflate a balloon
and fasten its mouth over the cork. Place the apparatus on a smooth
surface to see almost frictionless motion on cushion of air.
ANTI GRAVITY. Select two test
tubes so that one barely fits inside the other. Partly fill the
larger with water and float the smaller one on the water. Quickly
invert the tubes. As water leaks out, the smaller tube will rise,
apparently defying gravity.
BALL IN FUNNEL. Blow or suck
on the small end of a funnel containing a ping pong ball. The ball
will not fall out even though the funnel is inverted, so long as air
is moving between the ball and the funnel wall.
BALLOON ELECTROSCOPE. Light
rubber balloons suspended from long silk strings act as demonstration
electroscope. Charge the balloons by rubbing them with woolen cloth
or fur. When charged, balloons can be made to stick to flat surfaces
such as walls or ceilings.
BERNOULLI BALANCING ACT.
Bernoulli's principle can be shown by balancing an inflated balloon
or beach ball on a jet of air from the output end of a vacuum
cleaner. The balloon will hover near the ceiling and will not fall
off although tipped at a considerable angle. A ping pong ball
balanced on a fine jet of water will illustrate the same.
BIG TORQUE. Hold the end of a
broom handle in one hand and extend your arm and the broom handle
horizontally in front of you. Tie a string around a book and hang the
book under the stick a few centimeters from your hand. Try to keep
the stick horizontal while someone slides the book toward the end of
the stick. Although the weight of the stick and book do not change,
the torque increases. Lever arm has real meaning here.
BLACK BOX CONTENTS. Into a
small box, place small objects and seal box closed. Students can
examine box, blindfolded, and tell you: (a) How many pieces are in
the box. (b) the shape of the pieces. (c) How heavy the pieces are
(density). (d) How big the pieces are. (e) The color of the pieces.
By doing this the student has reason to believe that the scientists
may know something about the atom even though it has never been seen;
as he has not seen the objects in the box.
BOILING WITH ICE. Fill a flask
two-thirds full of water and bring it to a boil. Cork the flask and
invert it taking care that the hot water does not spill out. Place an
ice cube on bottom of flask. As the ice melts, the water begin to
boil again. If the flask is corked with a one-hole stopper with a
glass tube extended almost to the bottom of the flask, boiling can be
effected by reducing the pressure of the entrapped air. You can also
run cold water over the flask. Have the student feel the flask
temperature as the ice boils the water. of boiling water.
CHAIN REACTION. Arrange wood
matches closely on a soft board by means of straight pins placed
through them at their midpoint. Hold the board upright and ignite the
bottom match. The others will follow in turn to demonstrate a chain
CHIEF SOHCAHTOH. Sometimes it
helps to point out that the sine of an acute angle in a right
triangle is the side opposite over the hypotenuse; O/H, oh!. The
cosine is "ah". A well known trick is to recall the name of the
legendary American Indian physicist, "Chief Soh- cah-toa". (Sine is
opposite over hypotenuse; cosine is adjacent over hypotenuse; and
tangent is opposite over adjacent.
COLOR ABSORPTION. Using
colored pencils, draw a bird in a blue cage. Let the bird out of the
cage by covering the drawing with a red filter. Try other color
combinations to show the effects of color absorption by filters.
COLORED ROACHES. Many organic
substances, dead or alive, show interesting characteristics under
black light. Cockroaches are multicolored under ultra-violet light.
CONDENSATION OF WATER VAPOR. A
simple cloud chamber can be made from a gallon jug fitted with a
one-hole stopper with a short piece of glass tubing. Blow into the
jug through the glass tubing to increase pressure. Put finger over
end of tube and pull stopper, suddenly reducing the pressure. No
cloud is formed. If some smoke is introduced into the jug it provides
nuclei about which water vapor condenses. Repeat the performance and
watch the clouds form in the jug.
COTTRELL PRECIPITATOR. Attach
one lead from a spark coil to foil surrounding a glass tube of about
one-inch diameter. Extend a wire from the other terminal of the spark
coil through the tube, insulated from the foil. Place a small amount
of hydrochloric acid in one flask and some ammonium hydroxide in a
second flask. With glass tubing connect the flasks and large glass
tubing in train. Blow air into the first flask causing ammonium
chloride to be forced into the Cottrell precipitator. Activate spark
coil and see 'smoke' consumed. It works near instantly on cigarette
SHADOW REFRACTION. Place an
object on the bottom of a metal pan so that its shadow may be
measured. Fill the pan with water and remeasure shadow. Refraction is
evident if pan, object, and light source are kept stationary.
CRUSHED CAN. The force of
normal external air pressure is sufficient to collapse a rectangular
varnish can. In a clean can place a few tablespoons of water and
bring it to a boil to expel the air with the water vapor. Close the
cap tightly as soon as water boils vigorously. Cool the can by
dashing cold water on it. ... two comments: You don't need to run
cold water over the can. Be sure to stopper it very soon after you
remove the source of heat. If you don't, the reverse effect happens.
DENSITY OF ICE. Some
properties of water make interesting conversation pieces. Demonstrate
that ice is lighter than water by placing large icicle in milk bottle
(ice cubes may be used). Add cold water to fill jar while holding ice
under the water. Let ice float and observe how much water overflows
as the ice melts.
DIMPLES AND PIMPLES. Heat a
spot on a cold light bulb with a blow torch and a dimple will form in
the glass. Light the bulb and again heat a spot until a pimple forms.
DRY WATER. Let the student
explain why one can pick a coin from the bottom of a beaker of water
which has been dusted with lycopodium powder and not wet a finger.
EFFECT OF GAS DENSITY ON
SOUND. Fill several balloons with different gases such as
air, carbon dioxide, natural gas, helium, and propane to about the
same pressure. Fix a whistle to be blown to a short piece of glass
tubing. Note the pitch as gas from the different balloons blows the
ELEMENTARY BATTERY. Show emf
produced between solutions of different concentrations by using two
copper discs attached to insulated wire and suspended in a dilute
copper sulfate solution, then drop a few crystals of copper sulfate
in to make the bottom layer more concentrated. Connect the electrodes
to a sensitive milliammeter or galvanometer.
ENERGY CONSERVATION. Suspend a
bowling ball with a strong cord from the ceiling, Draw the ball back
against your nose, with your head against the wall. Release it and
stand nonchalantly awaiting its return. It cannot rise to greater
than height from which it started. You are save if you do not move or
push the ball during its release.
FISSION BUBBLE. Activation of
nucleus to fission may be demonstrated by catching a soap bubble
between two wire rings with handles. When caught, puncture the top
and bottom areas leaving a cylinder between the rings. Carefully pull
the rings apart, noticing the shape of the film, until it breaks in
two films over each circle.
FLAME DISCHARGE. Ionization in
a flame can be shown by holding a lighted match near a charged
electroscope. Charged pith balls or balloons lose their charge
rapidly when a flame is brought near.
GAMES Games can make both
learning and instruction a pleasure. Build puzzle of jumbled letters
for other students to solve. An example:
- CTVREO-- has magnitude and direction
- DSEPE -- magnitude portion of velocity
- OHNTPO-- elementary light wave
GROWING SILVER CRYSTALS. Place
a copper penny on the glass slide of a micro-projector. Put silver
nitrate solution around copper and watch silver crystals form on
screen. Note many peculiar characteristics they exhibit.
GYRO ASSEMBLY. Weld bicycle
axle nuts in end of iron pipes. Screw the pipes on wheel axle for
handles. This makes an excellent gyroscope; better when the rim is
weighted by winding it with iron wire.
GYRO BAT CIRCLES. Turn around
by swinging baseball bat in circles over head. Reversal of swing
reverses motion of body. (Standing on rotating platform.)
GYRO HOME RUN SWING. Show
action and reaction by standing on rotating platform and swinging a
baseball bat vigorously at a pitched ball. .... This should be
amusing- Do it outside, of course.
GYRO MOMENTS. Again on the
rotating platform, pirouette. Hold heavy weights at arm's length,
have someone rotate you slowly. Bring weights close to body. Explain
the marked increase in speed.
GYRO PLATFORM. Construct a
rotating platform from an automobile front-wheel and spindle.
Rigidness, coupled with small friction and small play in the bearings
is amazing. This is useful to demonstrate rotational inertia and
maneuvering in space.
GYRO PRECESSION. Holding gyro
axis horizontal, Stand on a rotating platform holding a spinning gyro
wheel with its axis horizontal. Observe what happens when the axis is
rotated to a perpendicular position to the right? to the left?
HAIR RADIO TRANSMITTER.
Combing the hair near the aerial of a radio produces static.
HEAT TREATMENT. The effect of
heat treatment and tempering of metals can be demonstrated by heating
bobby pins to redness in a Bunsen flame. Dip one heated pin in cold
water to chill. Allow the other pin to cool slowly. Compare these
pins with one that has not been heated by bending each one.
HOLY WATER. Can molecules of
water have spaces between them. Pour water into long test tube or
graduate until it is three-fourths full. Then completely fill it to
capacity with alcohol. Place your palm over the top of the container
and invert it. Be careful that no liquid is lost as the water and
alcohol mix. Observe that the container is no longer full. (Evidently
some alcohol has disappeared in water molecule holes.)
HOT DOG WHISTLE. Tune two
metal dog whistles to unison or absence of beats. Heat one whistle
with flame. Beats reappear as pitch of heated whistle rises. (please
don't burn your lips!)
HOT ROD BALANCE. Drill a brass
rod for a screw in one end. Insert screw about half way. Balance rod
at its center on a pivot. Throw off balance by moving small screw on
one end. Heat on end of rod and it will come to balance again.
HYDROSTATIC SCALE. Weigh
yourself by hydrostatic pressure. Use a hot water bottle with a
stopper fitted with about two meters of rubber and glass tubing. Fill
the bottle with water and connect the tubing so that it extends
vertically. Lay the bottle on the floor and cover most of it with a
small board of known area. Stand on the board and measure the
increased height of the water in the tube. Your weight is equal to
the area of the board times the water pressure increase. Calculate
the water pressure by multiplying the density of water ( 1 gram per
cubic centimeter) by the difference in the water level height when
you stand on the scale.
IMPULSE AND INERTIA MAGIC.
Done with a lot of flourish, this brings down the house! The
mechanics of friction, forces and inertia involved make interesting
conversation. Set a glass two-thirds full of water about three inches
from the edge of a table. On the glass place a pie tin. On the pie
tin and directly over the glass place a spool on end. Place an egg
(fresh if you are confident) on the spool. With one foot on the
bristles of a springy broom, pull back the handle and aim at the pie
tin. The spool rolls on the table, the pie tin scoots to the floor,
the glass and the water remain unmoved on the table with the egg
unharmed in the water.
LENZ'S LAW. Lenz's Law may be
demonstrated with any toy wheel of nonmagnetic material and low
friction attached to a convenient holder. Wheel should have spokes
for clearest understanding. Spin wheel in air then between poles of a
reasonably strong horseshoe magnet. Spokes cut lines of force,
induced current field opposes motion.
LOCATING THE CENTER OF GRAVITY.
Start with your hands outstretched and palms facing each
other about a meter apart. Rest a horizontal stick or metal pipe on
the index fingers of each hand. With your eyes blindfolded, slowly
move your hands together until the palms meet. Regardless of the
starting position of your hands, the center of gravity of the stick
or pipe will be at the point where your hands come together.
MAGNETIC WAVES. Suspend a bar
magnet on a string. Rotate another magnet under it to show transfer
of magnetic energy. What changes the direction of the poles? How can
the change be effected without human movement.
MASS SPECTROGRAPH. Properties
of alpha, beta, and gamma rays may be demonstrated by propping a
smooth board of about eight inches by twelve inches on an incline and
arranging a bin with a trap gate at the top so that three different
sized balls can be released to roll down the board. Place a strong
magnet below the board and just to one side of the gate. Note how
each falling ball goes into a separate bin because of the amount of
deflection. The gamma may be represented by a brass or aluminum ball,
he beta would be the smaller of the steel balls.
MATCH DISCHARGE. Rubber bands
or strips can be tied together in bundles and charged by stroking
with fur or by other means. A lighted match near the repelling
strands will cause them to collapse.
MATCH HEAD DIVER. A Cartesian
diver can be made with a Coca-Cola bottle full of water and a match
head. Keep breaking off the match stick until the head barely floats.
Thumb pressure on the mouth of the bottle makes these little divers
zip up and down in the bottle.
NEON SINE. Swing a large 115
volt neon bulb rapidly to show sine curve in space as alternate
NUT DRO Fix six or seven
metal nuts on a string at distances in proportion to 1/2 gt^2 where
the time is 1, 2, 3, 4, etc. seconds. Hold string vertical and still
and let drop. Note there is no difference in the time intervals as
nuts strike the floor.
PAPER KETTLE. Boil water in a
paper cup. The paper will not burn until the water has boiled away.
PAPER WEIGHT. Cover a wooden
slat with a sheet of newspaper except for a few inches which project
beyond the edge of a table. Hit the protruding part of the slat with
a sharp downward blow of a hammer. The slat breaks without tearing
PENCIL POINT BALANCE. To
demonstrate center of gravity outside of a body and the criterion for
stability, borrow two pocket knives from students. Push blades firmly
(but carefully) into a pencil near the sharpened end with the handles
beyond the point of the pencil. Balance the pencil point on your
finger. Since the system center of gravity falls below the point of
balance, the system is stable.
PINHOLE EFFECTS. An
interesting conversation piece can be made from an empty 35 mm film
can. In the center of one end punch one hole with a sharp needle.
About the center of the other end punch three pinholes at the corners
of an equilateral triangle about two millimeters apart. Look through
the one hole and see the three holes. Look through the other end at
the one hole and explain what is seen. Label the box "Drunk-O-Meter"
and list the following directions: 1 hole-sober, 2 holes-nipping, 3
holes-dog drunk, 4 holes or no holes at all -dead drunk.
POURING AIR. Submerge a beaker
full of water in a large water filled container or fish tank. Invert
the beaker so its open end is down. Invert a second beaker and
submerge it so that air is trapped inside. Pour air from one beaker
into another, pouring up. Note fluid nature of the gas.
POURING CARBON DIOXIDE.
Construct a series three 5-cm steps that will fit into a wide mouth
jar. Set a lighted candle on each step. Slowly pour carbon dioxide
gas from an open container into the jar. Carbon dioxide is heavier
than air. As it settles it extinguishes the candles one by one
starting with the candle at the lowest level. There are many ways to
generate carbon dioxide. Try mixing some vinegar with bicarbonate of
PRECISION IN ADVERTISING.
Encourage students to think, speak, and write more precisely.
Illustrate by using a meaningless advertising slogan: "The
Rolls-mobile is bigger and better: -than- (a) a diddie car (b) a
freight car (c) last year's model.
RATE OF HEAT CONDUCTION. Three
students each holding a rod of a different substance in a flame, will
demonstrate the difference in conductivity of heat by their object
from the flame. Use about the same sized rods of iron, aluminum,
REACTION OF THE ROAD. Place
plank on rollers (doweling). With string, tie a small cart to one end
of the plank and stretch a long rubber band between the cart and the
other end of the plank. Add weights to the cart to increase its mass.
Burn the string to release the system. The road goes one way, the
cart goes another.
RETINAL AFTER EFFECTS. Draw a
circle in the center of a piece of white paper with colored crayon.
Stare at the circle at arms length for a time, then look at a blank
wall. A circle of some other color appears on the wall.
ROLLING SPOOL. Select a large
spool and wrap several turns of ribbon or twine around it. Place the
spool on a table so it can roll when the free end of the ribbon is
pulled out from the spool bottom. Observe the direction that the
spool rolls when the ribbon is pulled straight up and when it is
pulled at other angles closer to the horizontal. With a little
practice, the spool can be made to roll in either direction as the
ribbon angle is changed. Encourage students to explain the phenomena
using terms such as torque, friction, and vector direction of force.
SEEING THE SUN BEFORE SUNRISE.
Evidence that one may see the sun while it is still below the horizon
can be visualized by looking at a penny at the bottom of a bowl
filled with water. Note that the penny cannot be seen over the rim of
the bowl unless there is water in the bowl. When the sun first
appears in the morning, it is still our of sight below the horizon.
Refraction of the sunlight by the atmosphere makes the sun appear
higher than it really is.
SELECTIVE IMAGE INVERSION.
Print with capital letters the word TITANIUM DIOXIDE. Use a red
pencil for the first word and a blue pencil for the second. View both
words through the side of a test tube filled with water. Only the red
word looks inverted.
SELECTIVE LIGHT SCATTERING.
Demonstrate the effect of the sun setting through the dust-laden
atmosphere. Add five grams of sodium thiosulfate and 5 mL of
concentrated hydrochloric acid to a liter of water in a clear
container. Shine a light through the solution and on to a wall or
screen. Observe the changes as the colloidal sulfur forms. Scattered
blue light can be seen in the solution at a ninety degree angle from
the beam. On the screen or wall the spot slowly changes from white to
yellow, to red, and then is finally is blacked out completely.
SINGING FLAME VARIATION. Hold
a four foot 1-1/2 inch glass tube vertical. Insert in the bottom end
at a predetermined resonance point a heavy disc of wire gauze. Heat
the wire gauze with burner, then remove flame and hear a phenomenon.
SINGING TUBES. A straight
metal blow pipe connected to a gas supply is fixed in an upright
position on the demonstration desk and lighted. A thirty to sixty
centimeter glass tube of large diameter is lowered over the flame
until at a certain position a sound is heard.
SKY HOOK. Cut a four inch
piece of wire from a coat hanger. Bend one half inch back on one end
so that a leather belt will slip in the hook. Rest the free end of
the wire on a finger tip. The belt and wire will hang out in space
without apparent support underneath.
SPINNING HAMMER. Mark the
center of gravity of a hammer with a spot of paint. Toss the hammer
into the air with a spin and note that the spot is the most
stationary point of the hammer as it spins.
STANDING WAVES ON A STRING.
Wave motion and standing waves can be demonstrated by attaching a
vertical string to almost any small electric motor or vibrator. An
electric shaver is ideal. Hang weights of varying amounts on the
string. As the tension increases, there will be changes in the length
of the standing waves.
UNLIMITED WATER SUPPLY.
Suspend a water faucet above a sink by a thin wire. Water can be made
to flow continuously in a strong stream from the faucet bottom
despite the fact that the faucet is not connected to any water pipes.
The secret is to use a concealed electric water pump that pushes
water up a glass tube into the bottom of the faucet. As the water
emerges, it flows over the outside of the glass tube concealing the
tube from view. This makes an interesting corridor display.
STEREOSCOPIC VISION. Look
through a paper tube at some distant object with the right eye while
holding a book over the other eye and close to the tube. It will
appear that one is looking through a hole in the book.
STRETCH CHARGE. Stretch a
rubber band tightly and rub against an electroscope. Determine the
nature of charge produced.
SUSPENDING SOAP BUBBLES. Show
that a soap bubble filled with air will float on carbon dioxide.
Using a bubble pipe or straw, blow a soap bubble and carefully place
it in the center of a jar partially filled with carbon dioxide.
Because the carbon dioxide is invisible the bubble appears to be
suspended without any support.
SWINGING PENDULUM. Show
conservation of energy in a swinging pendulum by noting that it
returns to the same level each time. Place an obstruction below the
point of rotation so that the arc of swing will be changed. Change
the obstruction to a point one half the distance between the lowest
and highest levels and again below this point. Explain why the bob
loops over the obstruction.
TUBELESS TELEVISION. Prepare a
slide with a few simple words such as THAT'S ALL cut in a piece of
metal foil. Aim the slide projector so the beam goes out an open door
and does not attract attention. In a darkened room, wave a white wand
in the plane where the image is focused. Persistence of vision
creates a complete image, apparently materializing the words in
VARIABLE DENSITY. Moth balls
rolled in sodium bicarbonate and put into a cylinder of very dilute
hydrochloric acid will rise and fall with regularity.
VARIABLE VOLUME SPONGE. A dry
plastic sponge can be measured for volume. Ask how much water you can
pick up with it. When wet, it may pick up more than its initial
volume. It expands slightly and is mostly a "lot of air holes
VISCOSITY REACTIONS. Let a few
students with egg beaters beat oils of different viscosity. Those
having to beat the heaviest oils will tire first.
VISUALIZED WORK UNITS.Mount a
12 inch length of 2x2 inch wood upright on a base. Mount another one
slightly over 9 inches long on the same base. Lifting a one-pound
weight from the base to the top of the one foot tower represents one
foot-pound of work. Lifting the weight to the top of the 0.76 foot
tower represents one joule of work. A feather lifted from the table
top on to a piece of paper laying on the table represents an erg of
work.A millionth of a millionth of an erg is called an electron-volt.
WATER GLASS SUCKER. Carry a
glass brim full of water up a ladder and press it to the ceiling. Ask
the "sucker" to push against the bottom of the glass with a long pole
while you climb down and put away the ladder and go on about other
business. If the ceiling is smooth, the student need not fear that
the glass will fall.
WHISTLE BEATS. Prepare two
small whistles with a screw in the end so that the length of the air
column can be adjusted for different frequencies. Attach the whistles
to a Y tube so that they can be blown simultaneously. When the pitch
of one is slightly different than the other, a low pitch "beat note"
WOOD'S METAL. Carve a spoon
mold in wood and fill with molten Wood's metal. The spoon will melt
in hot water, coffee, or tea. Save the mold to recast the spoon as
part of the demonstration.