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||<:25%>[:PiraScheme#Mechanics: Table of Mechanics]||<:25%>[:Newtons1STLaw: Mechanics (1F): Newton's First Law]||<:25%>[:Newtons3RDLaw: Mechanics (1H): Newton's Third Law]||<:25%>[:Demonstrations:Lecture Demonstrations]|| ||<:25%>[:PiraScheme#Mechanics: Table of Mechanics]||<:25%>[:Newtons3RDLaw: Mechanics (1H): Newton's Third Law]||<:25%>[:AppNewtonsLaws: Mechanics (1K): Applications of Newton's Laws]||<:25%>[:Demonstrations:Lecture Demonstrations]||

[:PiraScheme#Mechanics: Table of Mechanics]

[:Newtons3RDLaw: Mechanics (1H): Newton's Third Law]

[:AppNewtonsLaws: Mechanics (1K): Applications of Newton's Laws]

[:Demonstrations:Lecture Demonstrations]

Statistics of Rigid Bodies

PIRA classification 1J

Grayed Demos are either not available or haven't been built yet

1J10. Finding Center of Gravity

PIRA #

Demonstration Name

Abstract

1J10.09

center of gravity

Many examples of simple center of mass demonstrations.

1J10.10

map of state

Suspend a map of the state from holes drilled at large cities to find the "center of the state".

1J10.10

map of state

Sandwich of a map of the state between two plexiglass sheets and suspend from holes drilled at large cities to find the "center of the state".

1J10.10

map of Minnesota

A plexiglass map of the state is suspended from several points.

1J10.11

find the center of gravity

Use a chalk line on the plumb bob and snap it to make a quick vertical line.

1J10.12

hanging shapes

Use the plumb bob method to find the center of gravity of various geometric shapes.

1J10.12

hanging board

Suspend an irregular board from several points and use a plumb bob to find the center of gravity.

1J10.12

irregular object center of mass

Suspend an irregular object from several points and find the center of mass with a plumb bob.

1J10.15

hanging potato

Hang a potato from several positions and stick a pin in at the bottom in each case. All pins point to the center of gravity.

1J10.20

meter stick on fingers

Slide your fingers together under a meter stick and they meet at the center of gravity. Add a baseball hat to one end and repeat.

1J10.20

friction and pressure

Slide your fingers under the meter stick to find the center of mass.

1J10.20

meter stick on fingers

Slide your fingers under a meter stick to find the center of mass.

1J10.25

center of gravity of a broom

Bring your fingers together under a broom the find the center of gravity.

1J10.25

center of gravity of a broom

Find the center of gravity of a broom, hang a kg mass somewhere on the broom, find the new center of gravity, calculate the weight of the broom by equating torques.

1J10.26

balance beam and bat

1J10.30

meter stick on fingers

1J10.30

loaded beam - moving scales

Slide the scales together under a loaded beam noting the scale readings of the moving and stationary scales.

1J10.30

loaded beam - moving scales

Instead of moving the masses on the beam, move the scales under the beam. Same as bringing your fingers together under the meter stick.

1J10.41

your center of gravity

Two methods for measuring the center of gravity of a person are shown.

1J11. Exceeding Center of Gravity

PIRA #

Demonstration Name

Abstract

1J11.10

leaning tower of Pisa

Add a top to a slanted cylinder and it falls down. Also hang a plumb bob from the center of mass in each case.

1J11.10

leaning tower of Pisa

A model of the tower constructed in sections. Adding the top will cause it to tip over.

1J11.10

leaning tower of Pisa

Add on to the leaning tower and it falls down.

1J11.10

leaning tower of Pisa

The leaning tower of Pisa.

1J11.11

falling cylinders

A tube, weighted at the bottom, falls when a cap is added. An upright cylinder, containing two balls, falls when a weighted cap is removed.

1J11.11

toppling cylinders

The standard leaning tower and an upright cylinder that topples when the cap is removed. It has two balls in the tube.

1J11.12

irregular object center of mass

1J11.15

tipping block on incline

Raise an incline plane until a block tips over.

1J11.15

tipping block on incline

A very clever modification of the leaning tower of Pisa demonstration.

1J11.15

tipping block on incline

A block is placed on an incline and the incline is raised until the block tips.

1J11.20

leaning tower of Lire

Stack blocks stair-step fashion until the top block sticks out beyond any part of the bottom block.

1J11.20

leaning tower of Lire

Use 6"x6"x2' wood blocks and have a student sit under the stack as it is built.

1J11.20

leaning tower of lire

A note discussing the derivation of the harmonic series describing the leaning tower of Lire.

1J11.20

leaning tower of Lire

Use the center of mass of a composite object to support a block beyond the edge of the lecture bench. This article emphasizes a lab approach. Ref. AJP 23,240 (1955).

1J11.20

leaning tower of Lire

Stack blocks until the top block sticks out beyond any part of the bottom block.

1J11.21

cantilevered books

The number of books necessary to overhang 2,3,4, etc lengths.

1J11.30

instability in flotation

A device to raise the center of mass in a boat until the boat flips. Diagram.

1J11.40

people tasks, etc.

Pictures of three center of mass objects and several person based center of mass tasks e.g., stand on your toes facing the wall, etc.

1J11.40

male & female center of gravity

Stand with right shoulder and foot against the wall and raise your left foot. Stand with your heels against the floor and try to touch your toes.

1J11.50

double cone

As a double cone moves up an set of inclined rails, its center of gravity lowers.

1J11.50

rolling uphill

A simple version of a ball rolling up a "v".

1J11.50

double cone

A double cone rolls up an inclined "v" track.

1J11.50

double cone

Double cone and rails.

1J11.50

double cone

A double cone rolls up an inclined "v" track.

1J11.50

double cone on incline

The double cone appears to roll uphill.

1J20. Stable, Unstable, and Neut. Equilibrium

PIRA #

Demonstration Name

Abstract

1J20.10

bowling ball stability

A bowling ball is placed in, on, and along side a large plexiglass hemisphere.

1J20.11

balance the cone

A cone can show stable, unstable, and neutral equilibrium; a sphere shows only neutral equilibrium.

1J20.11

balance the cone

A large cone shows stable, unstable, and neutral equilibrium.

1J20.11

stability

Balance a cone, show a block is stable and a sphere is neutral.

1J20.12

wood block stability

A block and support have marks that show whether the center of gravity has moved up or down when the block is displaced.

1J20.15

block on the cylinder

A rectangular block of wood is placed on a cylinder first with the width less than the radius (stable) and then with the width greater (unstable).

1J20.15

block on the cylinder

An "elementary" discussion of the oscillatory properties of the block on the cylinder.

1J20.15

block on the cylinder

A thin block on a cylinder is stable, a thick one is not.

1J20.16

catenary surface

A large block is always in stable equilibrium anywhere along this catenary surface.

1J20.17

block on curved surfaces

A block is placed on a catenary surface, a circle, and a parabola.

1J20.20

fork, spoon, and match

Place a spoon and match in the tines of a fork and balance the assembly on the edge of a glass.

1J20.20

fork, spoon, and match

Picture of the fork, spoon, and match balanced on the edge of a glass.

1J20.20

fork, spoon, and match

Stick two forks and a match together and balance on a glass while pouring out the water.

1J20.20

fork, spoon, and match

Two forks and a match can be balanced on the edge of a glass while the water is poured out.

1J20.25

nine nails on one

A technique to balance ten landscape spikes on the head of a single upright spike.

1J20.30

sky hook

A complete solution to the hanging belt problem.

1J20.30

hanging belt

Shows a "belt hook" for the hanging belt.

1J20.32

spoon on nose

Hang a spoon on your nose. Most effective with giant food service spoons.

1J20.35

horse and rider

A horse has an attached weight to lower the center of mass.

1J20.35

horse and rider

Stable equilibrium of a center of gravity object.

1J20.35

horse and rider

A horse has a weight attached to lower the center of mass.

1J20.40

balancing man

Stable equilibrium of a center of gravity object.

1J20.40

balancing man

Stable equilibrium of a center of gravity object.

1J20.45

tightrope walking

Design of a 10' long "low wire" and description of the physical feats possible.

1J20.45

tightrope walking

A toy unicycle rider carrying a balancing pole travels along a string.

1J20.45

clown on rope

A toy clown rides a unicycle on a wire.

1J20.46

tightrope walking model

A model of a tightrope walker shows the center of mass moves up with tipping.

1J20.50

balancing a stool

Wires form a support at the center of gravity of a lab stool.

1J20.50

balancing a stool

Construct a stool so that wires crossed diagonally will intersect at the center of gravity. The stool can be oriented in any direction.

1J20.51

chair on pedestal

Hide heavy weights in the ends of a chair's legs so it will balance on a vertical rod placed under the seat.

1J20.55

broom stand

Spread the bristles and a straw broom will stand upright.

1J20.60

wine bottle

Stick the neck of a wine bottle through a hole in a slanted board and the whole thing stand up.

1J20.65

glass on coin, etc

Pictures show the hanging belt, pin on the point of a needle, and a jar balanced on its edge.

1J30. Resolution of Forces

PIRA #

Demonstration Name

Abstract

1J30.10

suspended block

Forces parallel and perpendicular to the plane will support the car midair when the plane is removed.

1J30.10

suspended block

A 3-4-5 triangle holding a block. Add counterweights and remove the incline.

1J30.10

suspended block

The components of force of a block on an inclined plane are countered by weights. The plane is then removed.

1J30.10

suspended block

A 5-6-7 suspended block system is used to show the pulleys can be moved as long as the angle remains constant.

1J30.10

suspended block

Forces parallel and perpendicular to the plane will support the car when the plane is removed.

1J30.10

load on removable incline

Place a cart on a removable 30 degree incline.

1J30.15

normal force

A block on an incline has an arrow mounted from the center of mass perpendicular to the surface with "N" on the arrowhead and another arrow hanging from the center of mass with a "g" on the arrowhead.

1J30.18

hanging the plank

A heavy plank is suspended from three spring scales in several configurations: series, parallel, and a combination.

1J30.20

tension in a string

The weight of a mass hung from a single spring scale is compared to the weight shown on a spring scale between two masses over pulleys.

1J30.20

tension in a string

A spring scale is suspended between strings running over pulleys to equal weights.

1J30.21

tension in a string

A clever story.

1J30.22

tension in a spring

Two students pull against each other through one and then two spring scales.

1J30.23

tension in springs

Masses are hung at the ends of a series of spring scales.

1J30.25

rope and three students

Two large strong students pull on the ends of a rope and a small student pushes down in the middle.

1J30.25

rope and three students

Two large strong students pull on the ends of a rope and a small student pushes down in the middle of the rope.

1J30.25

rope and three students

Two football players stretch a 10 m rope while a small person pushes the middle to the floor.

1J30.25

clothesline

Hang a 5 newton weight from a line and pull on one end of the line with a spring scale.

1J30.26

rope and three weights

Suspend a rope over two pulleys with masses on the ends and hang another mass from the center. Measure the deflection.

1J30.27

deflect a rope

Stretch a rope in a frame with a 100 newton scale measuring the tension. Pull down with a 20 newton scale.

1J30.30

break wire with hinge

Suspend a 5 kg mass from a length of wire. Break a length of similar wire by placing the same mass on the back of a large hinge.

1J30.30

breaking wire hinge

Pushing down on a slightly bent hinge will break the wire fastened to the ends.

1J30.30

breaking wire hinge

Press down on a hinge to break a rope.

1J30.35

pull the pendulum

A long heavy pendulum is displaced with a spring scale.

1J30.40

booms

A sprig scale measures the tension in the supporting rope at various loads and boom angles.

1J30.40

horizontal boom

The tension in the wire is measured with a spring scale for two different boom structures.

1J30.50

blackboard force table

Scales and masses are hung in front of a large movable whiteboard.

1J30.50

blackboard force table

A weight is hung on a string suspended between two spring scales.

1J30.50

blackboard force table

The standard blackboard force table.

1J30.50

blackboard force table

A mass is hung from the center of a cord attached to two spring scales. Start with the strings vertical, increase the angle.

1J30.50

blackboard force table

A force table in the vertical plane

1J30.50

force board

This looks like a magnetic vertical force board. A circle is marked with angles every 10 degrees.

1J30.51

vertical force table

A vertical force table that permits a continuous range of angles.

1J30.51

blackboard force table

A removable frame that sets on the chalk tray.

1J30.51

blackboard force table

A framework for doing the force table in the vertical plane.

1J30.52

force table on overhead

A plexiglass force table for the overhead projector.

1J30.52

force table on OH proj

Make a large sketch of the angles using the OH projector.

1J30.53

standard force table, etc.

The standard force table, three dimensional force table, and torque apparatus.

1J30.54

force table

Three scales and a ring to show forces add by parallel construction. Not the usual.

1J30.55

human force table

Sit on a chair that hangs from a chain attached to load cells on each end.

1J30.55

human force table

Hang from a large gallows frame on ropes attached to load cells.

1J30.55

bosun chair force table

Sit on a chair suspended from two supports equipped with protractors and commercial load cells.

1J30.57

blackboard force table - rubber band

Calibrate rubber bands for force vs. length, predict the mass of an object hung in a noncolinear configuration.

1J30.57

blackboard force table - rubber band

A simple substitute for scales is a calibrated set of rubber bands.

1J30.57

blackboard force table - springs

Use screen door springs in place of spring balances.

1J30.60

sail against the wind

Set a mainsail on a cart so it moves toward and away from a fan.

1J30.60

sail against the wind

Use a large fan to blow at an air track glide with a sail.

1J30.60

sail against the wind

A sail is mounted on an air track cart. A table fan supplies the wind.

1J30.60

sail and the wind

Apparatus Drawings Project No.4: A sailboat rides in an air trough which serves as a keel. Set the angle of the sail with respect to the wind.

1J30.60

sailing upwind (airtrack)

Use a skateboard cart with a foam core sail.

1J30.61

sail a trike against the wind

A wind driven tricycle moves against the wind.

1J30.64

sail against the wind

A wind driven boat accelerates against the wind. Description and Analysis.

1J30.64

sailboat and wind

A cork stopper boat with a keel and removable sail.

1J30.65

floating cork

A stick is hung by a thread at one end with the other attached to a cork floating on water.

1J30.65

floating cork

A stick is hung by a thread at one end with the other attached to a cork floating on water.

1J30.70

sand in a tube

Place a tissue on the bottom of an open glass tube, fill with a few inches of sand, and push down on the top of the sand with a rod.

1J30.70

sand in a tube

A couple of inches of sand held in a tube by tissue paper will support about 50 lbs.

1J30.75

stand on an egg

Three eggs in a triangle pattern in foam depressions between two plates will support a person.

1J30.75

egg crusher

A raw egg can be squeezed between two hard foam rubber pads with a force of over 150 lbs.

1J30.80

rolling wedge

A light roller lifts a heavy weight as it rolls inside an inclined hinge.

1J30.90

inverse catenary

A string of helium balloons tied at each end forms an inverse catenary.

1J30.91

catenary analog computer

Model the catenary on a simple analog computer.

1J40. Static Torque

PIRA #

Demonstration Name

Abstract

1J40.10

grip bar

A thin rod mounted perpendicular to a broom handle holds a 1 Kg mass on a sliding collar.

1J40.10

grip bar

Use wrist strength to lift a 1 kg mass at the end of a rod attached to a broom handle.

1J40.10

grip bar

Use wrist strength to try to lift 1 kg at the end of a rod attached perpendicularly to a handle.

1J40.10

grip bar

A thin rod mounted perpendicular to a broom handle holds a 1 Kg mass on a sliding collar.

1J40.10

torque bar

Use wrist strength to lift a weight suspended at various distances from the handle.

1J40.15

torque wrench

Modify a Sears torque wrench so weights can be hung at different distances.

1J40.15

torque wrench

A torque wrench is used to break aluminum and steel bolts.

1J40.16

different length wrenches

1J40.20

meter stick balance

Hang weights from a beam that pivots in the center on a knife edge.

1J40.20

torque beam

Hang weights from a beam that pivots in the center on a knife edge.

1J40.20

torque beam

Weights are hung from a horizontal bar pivoted on a knife edge.

1J40.20

torque beam

Weights are hung from a meter stick suspended on a knife edge.

1J40.20

torque beam

Weights on a meter stick supported at the center.

1J40.20

balancing meter stick

Use a meter stick, suspended at the center, as a torque balance.

1J40.21

hinge board

Use a spring scale to lift a hinged board from various points along the board.

1J40.23

torque beam

Put a quarter (5 g) on the end of a meter stick and extend it over the edge of the lecture bench until it is just about to tip over.

1J40.24

walking the plank

Place a 50 lb block on one end of a long 2x6 and hang the other end off the lecture bench. Walk out as far as you can.

1J40.25

torque disc

Weights can be hung from many points on a vertical disc pivoted at the center.

1J40.25

torque disc

Various weights are hung from a board that can rotate freely in the vertical plane.

1J40.25

torque wheel

Use a wheel with coaxial pulleys of 5, 10, 15, and 20 cm to show static equilibrium of combinations of weights at various radii.

1J40.26

torque disc

An apparatus to show the proportionality between torsional deflection and applied torque.

1J40.26

torque disc

Twist a shaft by applying coplanar forces to a disc.

1J40.27

torque double wheel

1J40.30

opening a door

1J40.30

opening door

1J40.32

opening a trapdoor

1J40.32

opening trapdoor

1J40.40

loaded beam

Move a weight along a 2X4 on two platform scales.

1J40.40

loaded beam

Large masses can be placed on a board resting on two platform balances.

1J40.40

loaded beam

A model bridge is placed on two platform scales and a loaded toy truck driven across.

1J40.40

loaded beam

A heavy truck is moved across a board supported on two platform scales.

1J40.40

bridge and truck

A plank rests on two spring scales forming a bridge. Move a toy truck across.

1J40.41

loaded beam

Support the loaded beam with spring scales instead of platform balances.

1J40.45

Galileo lever

Same as Sutton device.

1J40.45

Galileo lever

A simple device to demonstrate the law of moments.

1J40.45

Galileo lever

A simple device to show the law of moments.

1J40.50

Roberval balance

Large Roberval balance.

1J40.50

Roberval balance

A reminder and picture of the Roberval balance. Reaction to TPT 21, 494 (1983).

1J40.50

Roberval balance

A large model of the Roberval or platform balance.

1J40.50

Roberval balance

Neutral equilibrium is maintained at any position on the platform.

1J40.51

Roberval balance

A version of the Roberval balance where a rigid assembly has upper and lower arms on one side.

1J40.55

balances

The equal-arm analytical balance and weigh bridge.

1J40.56

balances

The steelyard.

1J40.60

suspended ladder

Model of a ladder suspended from two pairs of cords inside an aluminum frame.

1J40.65

hanging gate

A gate initially hangs on hinges, then add cords and remove the hinges leaving the gate suspended in mid air.

1J40.65

hanging gate

Construction and use of a model of the swinging gate.

1J40.70

crane boom

1J40.75

arm model

Place a spring scale on a skeleton in the place of the biceps muscle and hang a weight from the hand.

1J40.75

arm model

Use an arm model simulating both biceps and triceps muscles to throw a ball.

[:Demonstrations:Demonstrations]

[:Instructional:Home]

fw: RigidBodies (last edited 2020-11-12 16:07:36 by srnarf)