[:PiraScheme#Mechanics: Table of Mechanics]

[:RigidBodies: Mechanics (1J): Statistics of Rigid Bodies]

[:Gravity: Mechanics (1L): Gravity]

[:Demonstrations:Lecture Demonstrations]

Grayed out demonstrations are not available or within our archive and are under consideration to be added.

PIRA #

Demonstration Name

Abstract

1K10.10

Tipping Block

A spring scale is used to show the least force required to overturn a cube.

1K10.11

Tipping Block

Show the force necessary to tip over trapezoidal and weighted rectangular blocks. The students are surprised to discover the force needed is not related to the position of the center of mass.

1K10.20

Ladder Against a Wall

Set a model ladder against a box and move a weight up a rung at a time.

1K10.25

Forces on a Ladder - Full Scale

Wheels are attached to the top of a ladder and the bottom slides on the floor. Climb up the ladder and fall down.

1K10.30

Walking the Spool

Pull on a cord wrapped around the axle of a large spool. The spool can be made to go forward or backward depending on the angle.

1K10.31

Walking the Spool x three

Three rolling spools: the outer discs ride on rails and the center section with the string is larger, smaller, and the same size as the outer discs allowing one to always pull horizontally.

1K10.40

Pull the Bike Pedal

Lock the front wheel, remove the brake, add training wheels, and pull backwards on the pedal in the down position. Pulling backward on a pedal (in the down position) of a brake-less bike will cause the bike to go back unless the length of the pedal crank is increased.

1K10.41

Traction Force Roller

Pull on a string wrapped around the circumference of a cylinder on a roller cart. Pull on a yoke attached to the axle of the same cylinder on the roller cart.

1K10.42

Extended Traction Force

A string wound around a cylinder, hoop, and spool is pulled while the objects are on a roller cart and the reaction force direction is surprising.

1K10.50

Rolling uphill

A loaded disc is put on an inclined plane so it rolls uphill or rolls to the edge of the lecture bench and back.

1K10.80

Teaching Couples

Start with two index fingers rotating a meter stick about the center of mass, use it to go into couples. Read it.

1K10.81

Free Vector

A strong magnet on a counterbalanced cork always rotates about the center of mass no matter where the magnet is placed.

1K10.82

Couples

An arrangement to apply equal forces to opposite sides of a pulley mounted on a dry ice supported steel bar.

1K10.83

Air Jet Couple

Air from a balloon is released through two nozzles offset from the center of mass. The assembly is free to rotate on a block of dry ice.

1K10.90

One Person Teeter Totter

One person sits on one side of an unbalanced teeter-totter but is able to bring it into equilibrium by applying a torque to a bar placed across his shoulders.

PIRA #

Demonstration Name

Abstract

1K20.05

washboard friction model

1K20.10

friction blocks - surface material

Pull a block with four different surfaces with a spring scale.

1K20.10

friction blocks - surface material

A set of blocks with different surfaces are pulled with a spring scale.

1K20.10

friction blocks

Pull blocks across the lecture bench with a spring scale.

1K20.10

surface dependence of friction

Place brass blocks on an incline with four surfaces: teflon, wood, sandpaper, and rubber.

1K20.12

friction blocks

Several ways to move a surface under a fixed block.

1K20.13

sliding friction machine

A spring scale is attached to an object on a rotating table.

1K20.13

friction blocks

A device includes both sliding surface and mounted spring scale.

1K20.13

friction blocks

A block is constructed with an built-in apparatus to measure coefficient of friction directly.

1K20.13

friction blocks

An apparatus pulls a block at a constant speed and measures the frictional force. Details in appendix, p.550.

1K20.13

friction blocks

A block rests on a turntable and the string goes to a dynamometer.

1K20.15

weight dependence of friction

Pull a friction block with a spring scale, add a second equal block to the first and repeat.

1K20.15

weight dependence of friction

Add mass to a board pulled along the table with a spring scale.

1K20.16

friction blocks

A loaded cart rolls down an incline and hits a barrier. The load continues sliding on a second incline until it stops. The mass on the slider is varied to show stopping distance independent of mass.

1K20.17

friction blocks

Two additional points relating to Geoffery Fox's "Stumpers" column TPT. 11, 288 (1973).

1K20.20

area dependence of friction

A friction block has a rectangular shape with one side twice as big as the other. One of the smaller sides is routed out to 1/5 the area.

1K20.20

friction blocks

Friction independent of area of contact - cut a block to form a prism whose cross section is an irregular polygon.

1K20.20

area dependence of friction

A 2X12 is pulled along the bench top while resting on either the narrow or wide face.

1K20.30

static vs. sliding friction

Use a spring scale and block to show that static friction is greater than sliding friction.

1K20.30

static vs. sliding friction

Show that static friction is greater than sliding friction with a spring scale and block.

1K20.35

angle of repose

An incline plane is lifted until a block begins to slide.

1K20.35

angle of repose

Using the familiar suspended incline block apparatus to examine normal and frictional forces in sliding up and down the plane.

1K20.35

angle of repose

An inclined plane is raised until a block starts to slide.

1K20.37

tire friction

The automobile tire is a misleading example of static and sliding friction.

1K20.37

tire skid equation

Motivated by being an expert witness, An approximate expression for sliding friction coefficient as a function of speed was developed from published tables.

1K20.37

angle of repose

A plastic small parts drawer on a sanded aluminum surface allows weight to be added easily.

1K20.37

angle of repose

Using the incline plane for various friction demos.

1K20.38

how dry friction really behaves

A note arguing that the main rules of thumb about friction are wrong and the less said about friction the better.

1K20.38

angle of repose

A tribometer with a meter stick mounted vertically 1 m from the hinge gives a reading of coefficient of friction directly.

1K20.39

angle of repose

Glass - glass angle of repose with oil and oil/water.

1K20.39

angle of repose

The standard inclined plane and blocks + an interesting towel on a glass tube demo.

1K20.40

front and rear brakes

A model car is rolled down an incline with either front or rear brakes locked.

1K20.40

front and rear brakes

Construction details for a model car in which pulling a pin applies front, rear, or both sets of brakes to a car rolling down an incline.

1K20.40

front and rear brakes

A car slides down an incline with either front or rear wheels locked.

1K20.40

front and rear brakes

A car rolls down an incline with either front or rear wheels locked.

1K20.40

front and rear brakes

A toy car is modified so either the front or rear brakes can be locked. Slide down the incline plane for each case.

1K20.40

stability of rolling car

A toy car slides down an incline with either front or rear wheels locked.

1K20.42

friction roller

A cylinder in a yoke can be rolled or locked and slid as it is pulled by a spring scale.

1K20.42

friction roller

A cylindrical roller is pulled or slid across the lecture bench with a spring scale.

1K20.42

friction roller

A cylinder is pulled along and perpendicular to its axis by a yoke with a spring scale.

1K20.45

frictional force rotator

This article shows how to rotate a friction vector to make its component in a given direction as small as desired. Everyday unconscious applications of this method are presented along with some new demonstration equipment.

1K20.46

cross friction

Push a block across the slope of an incline and the block will move with a straight line trajectory. Knock a coin across and it will move in a curved path but all stopping points will be in a straight line.

1K20.55

squeaky chalk

You don't have to break chalk to eliminate squeaking, only understand friction and hold the chalk accordingly.

1K20.55

angle of friction with pencil

Tilt a pencil until it slides along the table.

1K20.60

sliding chain

Hang a chain over the edge of the table until the weight of the chain makes it slide.

1K20.70

falling flask capstan

Attach a 4 liter r.b. flask at the other end of a ball on a string and drape the flask over a horizontal rod 4' high. Let go of the ball.

1K20.70

falling keys capstan

A short analysis of the falling key capstan.

1K20.70

falling keys capstan

Hang a set of keys from a string draped over a pencil and when the string is released, the keys don't hit the floor.

1K20.71

discussion of the capstan

Friction experiments with the cord wrapped around a cylinder. Discussion of the donkey engine and capstan with a digression on sea chanties.

1K20.71

capstan on a force table

Tap a hole in the center of a force table and insert a bolt to use as a capstan.

1K20.71

capstan

Theory of the capstan along with discussion of applications.

1K20.71

capstan

Show the frictional force vs. the number of turns around a rod.

1K20.74

friction pendulum

A ball is suspended by a loop of string over a slowly turning horizontal wooden bar. A large amplitude results.

1K20.76

going up a tree

Very clever device. Look it up as its hard to describe.

1K20.80

Snoek effect

If you don't know about the Snoek effect, don't ask me - I had to read up on it too.

1K20.85

WWII torpedo story

Friction caused dud torpedo in WWII.

1K20.90

air track friction

Show there is little friction on an air track.

1K20.95

teflon cookie sheet

Cut up a teflon coated cookie sheet for an inexpensive teflon surface.

1K20.95

teflon pulley

Teflon sheet bent around corner replaces a pulley.

1K20.95

Dylite beads

Dylite beads on a rimmed glass surface (window pane) provide a low friction surface.

PIRA #

Demonstration Name

Abstract

1K30.10

bed of nails

Lie down on a bed of 16d nails on 1" centers.

1K30.10

bed of nails

Lie down on a bed of 16d nails on 1" centers.

1K30.10

bed of nails

The instructor lies on a large board with nails at 1" centers.

1K30.10

bed of nails

Break a block on the chest of a person lying on a bed of nails.

1K30.20

pop the balloons

A disc with points on one side can be placed on balloons so either the points or flats rest on the balloons.