Physics 102 Lecture Demonstrations

Demo
Topic
Short Name
UMd
Materials
Long Description

1

Atoms-01

Atoms
Homeopathy

3 Gallon jugs clean water
3 eye-droppers
Colored liquid (eg: Coke)
Clear plastic cup
Make a homeopathic sleeping drug. Put one drop Coke in first gallon. Mix well ('succuss'). Put one drop in 2nd gallon. Mix well. Put one drop in third gallon. Mix well. Pour into cup.

2

Density-01

Density
Density

3 equal weight but different density masses.
0.5 kg Fe, Al and wood
Display (round) spring scale.
Weigh the items to show they have the same weight.
Display the items to show they have different volumes.

3

Pressure-01

Pressure
3 egg stand

3 plastic beakers
Blue triangular wooden plate
Sand
4 eggs (raw)
Paper towel and broom and dustpan
Beaker to break an egg into (prove it's raw)
Fill beakers with sand. Shake to pack the sand. Place eggs in them pointed end down with half the egg buried.
Place beakers on paper towel on hard floor.
Place wooden plate on beakers so the eggs are under the corner pads.
Stand on the plate very slowly (it helps to have something to lean on). Make sure the eggs don't shift.

4

Pressure-02

Pressure
Seat of Nails

Seat of Nails
Sit on it.

4a

Pressure-02

Pressure
Starter Seat

1-Nail Seat of Nails
Get volunteer for SoN(4). Then bring out the Starter Seat and ask them to start with just one nail. Watch reactions!

5

Pressure-03

Pressure
Equal Height Tubes
F1-06
Equal Height Tubes
DARK Colored liquid
Pour liquid into tubes. All liquid levels are at the same height, since all have the same pressure at the base of the tube.

5a

Pressure-04

Pressure
Pascal's tube

Pascal's pressure tube demo
Dark water to fill it with
camera to display it??? Put in colored water
push in the plunger
watch water squirt out of all the holes in the end

6

Buoyancy-02

Buoyancy
Buoyancy Force

Large water beaker with at least 6" of water
Round visible Spring scale
masses of different materials (from demo #2)
Weigh the masses in the air
Weigh them in the water
The difference is the buoyancy force.
Larger objects have a larger difference

7

Buoyancy-01

Buoyancy
Float/Sink

Water tank
Different materials
What floats? What sinks?

8

Pressure-05

Pressure
Drop Holey Cup

3 Styrofoam cups or predrilled plastic cup
water
pen to puncture the cup
bucket to catch the cup
Puncture a styrofoam cup and the water will drain out.
Puncture it and drop it. Will the water drain out?
If you use the predrilled plastic cup, make sure there is water in the bucket to soften its landing

9

Buoyancy-03

Buoyancy
Al foil sink or float

water tank
Aluminum foil
Ask class whether Al foil sinks or floats. If they choose sinks, make a boat and float it. If they choose floats, place a sheet under water and watch it sink. Note that crumpled Al foil floats!

10

Buoyancy-04

Buoyancy
Finger in Beaker

pan balance
beaker of water
weights to balance
small sinker and floater weights
Put beaker of water on pan balance. Balance it.
Query: if add sinker (eg: metal), will the beaker go up, down or stay the same? Do it.
Query: if add floater (eg: wood), will the beaker go up, down or stay the same? Do it.
Query: if put finger in water without touching beaker, will the beaker go up, down or stay the same? Do it.

10a

Buoyancy-05

Buoyancy
Boat and Rock
F2-05
Fish tank half-filled with water
Tape to mark water level
Cut-out soda bottle (2-liter!!!) with screw-top
4 0.5-kg weights
Place weight in bottle (the boat) in the water so it floats.
Ask class: What will happen to the water level when the rock is dumped overboard?
Dump the rock overboard.

11

Buoyancy-06

surface tension
paper clip float

paper clip
petri dish of H2O

11.5

Air Pressure-01

Capillary action
Capillary Action
F3-11
Capillary tubes with green water, TV camera.
Four glass tubes of different diameter are connected at the base. The height of the water in each tube is determined by the effects of surface tension. The water is spiked with green food coloring to enhance its visibility.

12

Air Pressure-02

air pressure
break ruler w/newspaper

1/8"x3/4"x24" fibreboard
newspaper
place fibreboard so about 4" projects over end of table. Place newspaper over fibreboard. Smooth the paper over the board. Hit exposed end of board hard! Practice first.

13

Air Pressure-03

air pressure
magdeburg spheres

Magdeburg spheres
vacuum pump

14

Air Pressure-04

air pressure
soda can crush

Empty soda cans
large container of water
tongs
propane torch and ignitor
small cardboard square
Put about 1 oz of water in soda can and jam cardboard square under the pull tab to cover the hole. Ignite propane torch.
Grab can with tongs near the bottom. Tilt can and hold bottom corner over torch to boil the water.
Wait until lots of steam comes out of the can.
Quickly place can upside down into water container. Crunch!

14.5

Air Pressure-05

air pressure
vacuum cannon
I3-18
Vacuum cannon (ours is white PVC and about 6' long)
vacuum pump
heavy duty Al foil
ping pong ball
screw driver
Cover bottom end of vacuum cannon with Al foil and secure it with the hose clamp.
Drop the ping pong ball down the cannon barrel.
Place the soda can bottom over the top end of the cannon.
Attach the vacuum pump to the vacuum cannon.
Point the cannon away from people (or at a target).
Turn on the vacuum pump.
If the Al foil does not rupture spontaneously, poke it with the screwdriver.

15

Air Pressure-06

air pressure
reverse balloon inflate

Reverse balloon inflator

16

Air Pressure-08

air pressure
cup of water w/cardboard lid

Cup of water with even rim
3-4" cardboard square
Fill cup with water. Place cardboard over top. Invert. Air pressure holds the cardboard in place.

16a

Air Pressure-09

air pressure
holey cup of water w/lid

solid clear plastic cup with even rim and 1/4" hole on the side near the base
3-4" cardboard square
bucket
Cover hole. Fill cup with water. Place cardboard over top. Announce that the water is trapped. Wait for protestation. Flip over but keep hand over cardboard. Finally remove the cardboard.
Announce abracadabra and move finger from hole (make sure you're over the bucket)

17

Buoyancy-07

compress air
squiddy

squiddy
cup of water
sealable soda bottle w/water
Place squiddy in cup of water. Adjust buoyancy by squeezing to let water in until barely bouyant.
Place squiddy in water bottle and cap it.
Squeeze bottle to make squiddy sink.

18

Air Pressure-10

air pressure
bottle glug glug

full water bottle (narrow neck)
bucket
Pour water from bottle. It goes glug glug. Air pressure keeps the water from pouring in a steady stream.

19

Air Pressure-11

air pressure
tornado tube

two soda bottles
tornado tube coupling
water
Water does not go from top bottle to bottom unless you give it a swirl to start a vortex.

20

Air Pressure-07

compress air
vacuum balloon expand

small balloon
vacuum pump
bell jar
place small balloon in bell jar.
pump down.

21

Air Flow-01

bernoulli
alligator eyeballs

alligator eyeballs
place two small balls in eyecups
blow through mouthpiece constantly to 'levitate' the eyeballs
disinfect mouthpiece

22

Air Flow-02

bernoulli
funnel, tube and ping pong balls
F5-05
small funnel
long tube
PP ball
attach tube to narrow end of funnel. Hold funnel upside down. Hold ball inside inverted funnel. Blow hard through tube to keep the ball in the funnel.
Takes practice!
This is NOT due to the bernoulli effect, but the Coanda effect. See the UMd website for details.

22a

Air Flow-03

bernoulli
straw, spool, pin and card
F5-07
bendy straw
thread spool
straight pin
index card Place the straight pin through the center of the index card
bend the flexi-straw 90 degrees and put the short end through the center of the thread spool (so the end is flush or slightly recessed)
Place the card on the spool so that the pin rests in the straw
(a) card on top of the spool (blowing up): distribute lots of these to students and offer a large sum of money to the first student who can blow the card off the spool by blowing through the straw
(b) card underneath the spool (blowing down): blow hard to keep the card from falling. This is a much easier bernoulli demo than the previous demo.

22b

Air Flow-04

Bernoulli
bottle mouth and ping pong ball

cut off the top 2in of a plastic drink bottle
ping pong ball place the ping pong ball in the bottle top
challenge students to blow hard enough to blow the ball out of the bottle top (blowing upwards)
it also works blowing downwards (see 22) but you run out of air very quickly because the aperture is too big

23

Air Flow-05

bernoulli
bernoulli car
F5-01
bernoulli car
small styrofoam ball
Wind up car.
Place ball on smokestack. (Ping pong ball will NOT work)
turn on.

24

Air Flow-06

bernoulli
blower and ball
F5-06
air track blower
hose with contriction or nozzle
medium styrofoam ball
Turn on blower
Place ball in airstream
release.
tilt or move blower (slowly)

25

Air Flow-07

bernoulli
blow over paper sheet

paper sheet
hold one end of a sheet of paper in front of and below your mouth.
Blow over it (or slightly down)
watch it rise up.

26

Air Flow-08

bernoulli
blow between 2 balls

two large balls suspended by 2 strings
blower
blow between the balls
they move closer to each other

27

Air Flow-09

bernoulli
blow over airfoils

blower
hose without nozzle or constriction
various Al airfoils
blow over flat and airfoil shaped pieces of Al
which rises more?

27a

Air Flow-10

bernoulli
bernoulli bags

bernoulli bags (tie off one end on each)
get two students,
ask them each to inflate a bag
show the smaller one how to cheat

28

Air Flow-11

magnus effect
curve balls

curve ball thrower
medium styrofoam balls
The curve ball thrower is a 12" long, 4" diameter half-pipe with sandpaper inside.
Place a ball near one end of the thrower. Throw it like in Jai Alai. Watch it curve. A lot!

29

Heat Capacity-01

heat capacity
boil water in paper cup

paper cup
tongs
propane torch
ignitor
fire extinguisher
water bucket
fill cup with water, hold with tongs in flame of propane torch
(Hold over water bucket for safety)
don't use too much water or it will take forever to boil!

30

Thermal Expansion-01

thermal expansion
ball and ring
I1-12
metal ball w/handle
metal ring w/handle
propane torch, igniter, extinguisher
ball will fit through ring when both are at the same temperature
when heated, the ball no longer fits through

31

Thermal Expansion-02

thermal expansion
ball and plate
I1-11
metal ball w/handle
metal plate w/handle
propane torch, igniter, extinguisher
ball will not fit through plate when unheated
heat plate. Will ball fit through?

32
thermo
Liquid Nitrogen

lots o' stuff

33

Oscillations-01

waves
pendula

lab stand w/horizontal bar
two longer strings (w loop on end) must be equal length
1 shorter string (w/loop)
various masses
compare same length pend w/ different masses
compare different length pend w/ same masses
compare same length pend w/ same mass but different amplitudes

34

Oscillations-02

waves
BB pendulum

Bowling Ball pendulum
measure the period

35

Oscillations-03

waves
mass on spring

spring hanging from support
mass to hang from it
show that the motion is oscillatory

36

Oscillastins-04

waves
wave machine

wave machine
damper
reflector
show waves

37

Oscillations-05

waves
racing pendula

two rigid identical pendula with adjustable height masses
race them!

38

Waves-02

waves
slinky

slinky (long and short)
show longitudinal waves

39

Waves-03

waves
standing waves

loudspeaker with attached clip
frequency generator
string attached to lab stand, connected to clip, going over pulley
lab stand, pulley
weight hanger
weights
Strobe light
Stretch string horizontally from lab stand (on one end of lab table) over pulley and then down. Put weights on weight hanger on end of string (use enough weight to get the fundamental to a reasonable frequency). Attach loudspeaker via clip to the string near the lab stand. Connect frequency generator to loudspeaker.

Find the resonances
Show that the harmonics are multiples of the fundamental
pictures: one, two, three

39b

Waves-04

waves
same

same (but w/o loudspeaker)
Put a paper 'hanger' at the 3/4 point.
Hold the 1/2 point. Pluck the string at the 1/4 point.
What happens to the hanger?
Repeat for higher order.

39c

Waves-05

waves
Stringin' it

Stringin it demo
strobe light
black backdrop for demo adjust motor frequency to get standing wave
adjust strobe frequency to freeze the wave
(use either native strobe or external brighter strobe)
show that the frequencies of different resonances are simply related

40

Waves-06

Sound-04

sound
doppler ball

doppler ball
swing it around in a horizontal circle.

41

Sound-01

sound
buzzer in vacuum

buzzer in vacuum
vacuum pump
turn on buzzer, listen to it
pump air out of bell jar, buzzer gets much fainter

42

Sound-04

sound
flame tube (not done)

flame tube
gas bottle
frequency generator
match
fire extinguisher
flow gas thru tube. Make sure all air is purged from tube.
Ignite flames with a long match.
Connect freq gen to speaker. Find standing waves.
Do this away from drafts and breezes.

43

Sound-02

sound
paper cup telephones

Two paper cups joined by string
you know what to do

44

Sound-05

sound
tuning fork in water

tuning fork
cup of water
strike tuning fork.
quench by putting in water.
vibration of fork makes water spray.
need to carry around the room or put on camera (hard to see)

45

Sound-06

sound
trumpet in soap solution

PVC pipe and oil change funnel 'trumpet'
dish (Al pie plate) of bubble soap
bubble soap
paper towel
funnel to put excess soap back in container
Put bubble soap in pie plate
insert PVC pipe into funnel to make the trumpet
dip the trumpet bell into the soap solution and blow slightly to make the bubble protrude
sound the trumpet! The bubble vibrates but does not pop.
Practice beforehand!

46

Oscillations-06

resonance
resonance demo

resonance demo
This demo has three different length pairs of vertical rods with weights on the top.
Start one rod moving and only its partner will start moving too.

46a

Oscillations-07

resonance
many pendula

2' rod
five lengths of string (8", 12", 16", 20", 24") hanging from the rod with equal weights attached (50-100 g each)
Hold the rod horizontally in one hand with the five pendula hanging down.
Tell class that you can make any one weight swing just using the power of your mind. Concentrate on that weight. Make it swing by moving your hand slightly in resonance.
Practice first.

47

Oscillations-08

resonance
BB pendulum and mallet

Bowling Ball pendulum
rubber mallet
Hit the BB at the resonant frequency. It will start to move.
Quiz: will it move faster if I hit it more often?
Hit the BB at a much higher frequency. It doesn't move much.

48

Sound-07

resonance
different length tubes

Different length PVC pipe instruments. Can bring pan pipes, recorders, trumpets of various lengths
longer tubes make lower notes. It doesn't matter how they are blown (recorder mouthpiece vs pan-pipe vs 'trumpet'). Note that it can be quite hard to reach the fundamental on the recorders.
Practice first!

49

Sound-09

beat freq
slide whistle beats

Two slide whistles
Pull both slides all the way out.
Blow both whistles simultaneously.
Adjust one slide to get a good beat frequency.
Cheap, easy, reliable!
harder to show on Oscope.

50

Sound-10

beat freq
looudspeaker beats

Two loudspeakers
Two frequency generators
Adjust the frequencies to get beats.
Can show on Oscope.

50a

Sound-11

interference
sound cancellation

stereo with two loudspeakers
some recording or other
wire one speaker backwards
place both speakers face to face
sound is louder when one speaker is disconnected than when both are connected and cancelling!
Try this first to see what kind of music will work best.

51

Sound-12

harmonics
harmonics

PVC recorders
blow harmonics. practice beforehand!
blow taps or other bugle calls?

52

Sound-13

music
PVC instruments

Different length PVC pipe instruments. Can bring pan pipes, recorders, trumpets of various lengths
blow them. See them on the Oscope.

53

Sound-14

music
Oscope and mike

Oscilloscope
Microphone
visual presenter
Make sure presenter can see the scope.
Play lots of different instruments. Sing. Talk.
See waveforms on scope.

53a

Sound-15

music
Oscope and mike

laptop
Audacity or other software
Acquire waveforms with audacity and display to class
Play lots of different instruments. Sing. Talk. Show beat frequencies.
See waveforms on scope.
Use FFT to show frequency spectrum

54

Sound-08

music
straw oboe

straws
scissors
instruction sheets
make straw oboes
play

55

Color-01

color
black box

box with small aperture,
inside of arbitrary color
show that aperture looks black

56

Color-02

color
diff glasses +
vapor lamps

diffraction glasses
various vapor lamps
show the spectral lines that make up the various colors

57

Color-03

color
diff glasses +
incandescent lamp

diffraction glasses
incandescent lamp
put on glasses, look around, see rainbows
look at lamp, see complete rainbows
look at flourescent lights, see incomplete rainbows
white light is made up of lots of colors.

57a

Color-04

color
diff glasses and filters

diffraction glasses
color filters (cyan, yellow and magenta)
place filter on overhead. Use paper to mask all but a narrow vertical stripe
use diff glasses to see the colors transmitted by the filter
works great for cyan and yellow, less well for magenta
Need to show students what they are looking at.

58

Color-06

color
3 color lamps

RGB spotlights
various colored objects
Cyan, yellow and magenta filters
TEST SPOTLIGHTS BEFORE USING FOR COLOR BALANCE! DIMMER SWITCHES ARE USELESS!
TEST OBJECTS TO SEE HOW THEY APPEAR IN THE VARIOUS LIGHTS!
follow Hewitt's skit for showing color addition (see instructor manual)
start with white light, then show single colors and pairs of colors
show different color shadows
show colors of different objects in the spotlights
show colors of C, Y, and M filters in the spotlights (both reflected and transmitted)
PLAY!

59

Color-07

color
color wheel

color wheel on cordless drill
spin it and see white

60

Color-08

color
flashing pendant

flashing pendant
pendant appears white
swing it around and you see RGB
demonstrates a) color persistence and b) color addition

60a

Color-05

color
laser and filters

Red and green lasers
Red and grean and blue filter (eg: red food coloring in water in glass, same for green and blue)
CYM filters
What happens to red light shown through a red filter?
shine red laser through red filter onto screen in dark room. Some is reflected, some is transmitted)
What happens to red light shown through a blue filter?
shine red laser through blue filter onto screen in dark room. It is absorbed.
Try other combinations.

61

Reflection-01

reflection
standing mirror

standding mirror
2 volunteers
1 volunteer stands at mirror, adjusts slides until the second vol can see her entire height
vol 2 now moves a lot closer (or further)
How much mirror does she need now?

62

Reflection-02

reflection
small planar mirrors

small planar mirrors
hand them out.
look at self in mirror.
close one eye. How much of head do you see?
You want to see more. Move mirror?

63

Reflection-03

reflection
curved mirrors

curved mirrors
hand them out. look at self.

64

Reflection-04

reflection
mirrors reverse?

dark rear projection screen
Ask class: what direction do mirrors reverse?
Face mirror.
Hold out left arm. Is it on the audience's right?
Hold out right arm. Is it audience's left?
Do same for top/bottom
Point into mirror. Which way does the image point? Out!

65

Refraction-01

refraction
rod in beaker

rod in beaker of water
(have several to pass around)
see 'break' in rod

66

Refraction-02

refraction
coins in beaker

coin in small beaker of water
(have several to pass around)
look directly down at coins
hold hand by side of glass at the same perceived depth
compare to actual depth

67

Reflection-05

refraction
optical fibers

laser
optical fibers
shine through

67a

Reflection-06

refraction
optical fiber toy

optical fiber toy
light it up

68

Reflection-07

refraction
lucite spiral

lucite spiral
laser
shine through

69

Reflection-08

refraction
laser waterfall

laser waterfall
laser
water
catch basin
lab stand
support laser on lab stand or lab jack so it shines on the plug in the waterfall tube
fill tube with water
darken room
turn on laser
pull plug
makes sure the water lands in the catch basin

70

Reflection-09

refraction
flashlight waterfall

pickle jar with large hole (for water) and smaller hole (for air) in the lid
flashlight
catch basin
cover the pickle jar with dark paper so the paper extendsbelow the bottom
fill with water and screw on the lid
hold the flashlight pointing at the (unmasked) bottom
tilt and let the water pour out

71

Lenses-01

lenses
various lenses

various lenses
pass them around

72

Lenses-02

lenses
image of light on wall

spotlight
mask with asymmetric hole
lens
screen
place mask on spotlight
shine on screen
place lens between to focus the image on the screen
Will covering half the lens block half the image? Which half?

73

Diffraction-01

diffraction
diffraction

laser on lab jack
slide with a) single slits, double slits, diffraction grating
shine laser through slide onto far wall
darken room

74

Polarization-01

polarization
polarizing sheets

3 polarizing sheets
a) show one blocks some light
b) show a second blocks from 0-100% additional light
c) show crossed pol pass no light
d) show adding a third sheet between crossed pols lets light through
e) hold filter in front of computer projector. Show different colors polarized differently.

75

Polarization-02

polarization
rope and cooling rack

thin rope
two oven cooling racks
tie one end of rope down
get volunteer to hold cooling rack
shake rope - only 1 direction of shake gets through
crossed racks let nothing through

75a

Color-09

Flourescence
flourescent dies

UV lamp
flashlight
various flourescent dies
show dies in normal light
turn off room lighting
show appearance of dies under UV lamp
show same under flashlight

76

Nuclear-01

nuclear
geiger counter

geiger counter
something radioactive
let students hear clicks
try radioactive material (SEAL tritium watch, radium watch, Uranium glazed plate ...)

77

Nuclear-02

nuclear
cosmic ray telescope

cosmic ray telescope
let it count

78

Nuclear-03

fusion
double ball drop

Basketball
tennis bass
drop tennis ball
drop basketball
drop balls together with tennis ball on top (watch out!)
model of supernova with core collapse and rebound blowing off the outer layers

79

Quantum-01

Photoelectric
not made yet
Photoelectric effect in zinc
p2-02
Piece of zinc
electroscope
UV or arc lamp
material to charge the zinc positive or negative attach zinc plate to electroscope (see UMd set up)
charge plate positive
shine UV light on it (no discharge)
charge plate negative
shine UV light on it (discharges)
put glass plate between plate and light (no discharge)
See UMd web site for demo hints and interactivity hints