Mechanics
Measurement
Standards of Mass
PIRA: 1A10.20
Description: The objective of this demonstration is to familiarize the students with the metric measurement of mass, the kilogram. Show the students the 1 kg mass. Then pass it around the room. Let the students know that 1 kg is approximately equal to 2.2 lbs.
Meter Stick
PIRA: 1A10.35
Description: The objective of this demonstration is to familiarize the students with the metric measurement of the length, the meter (metre). Most, if not all, of the students have seen a meter stick so there would be no reason to pass it around. This would be an excellent time to discuss the standardization of units.
Time — The Pendulum
PIRA: 1A10.43
Description: The objective of this demonstration is to familiarize the students with the metric unit of time, the second. Use the pendulum to demonstrate how a unit of time was established. The string would be1m in length so that the period would be 2 seconds, that way it would be one second over and one second back.
Liter Cube
PIRA: 1A10.50
Description: Wooden block– 10 cm. x 10 cm. x 10 cm. — ruled at 1 cm. intervals. Volume
Coordinate System
PIRA: 1A30.10
Description: This demonstration is to show the students what is meant my vector components (ie. the x, y, and z components of a vector). Coordinate System
Rotating Vector (vector addition)
PIRA: 1A40.31
Description: Three vectors are cut from different color Plexiglas and set in a rotatable frame so that two vectors add head-to-tail, and the third vector represents the sum. The apparatus can be placed on the overhead projector so that the class can see that two vectors of equal magnitude do not always have the same sum. Vector Addition
The “Right Hand”
PIRA: 1A40.36
Description: Three axes of three-dimensional space have two possible orientations. One can see this by holding one’s hands outward and together, palms up, with the fingers curled, and the thumb out-stretched. For right-handed coordinates the right thumb points along the Z axis in the positive direction and the curl of the fingers represents a motion from the first or X axis to the second or Y axis. When viewed from the top or Z axis the system is counter-clockwise. Right-Hand Rule
Radian Measure with the Bike Wheel
PIRA: 1A50.11
Description: The length of an arc of a unit circle is numerically equal to the measurement in radians of the angle that it subtends; one radian is just under 57.3 degrees. Radian
Parabolic Path
PIRA: 1A50.12
Description: The parabolic path of projectile motion can be demonstrated by shooting a stream of water upward and outward.
Powers of Ten
PIRA: 1A60.10
Description: “Powers of Ten” is a 9 min. film covering scales from the universe to sub-atomic.
Motion in One Dimension
Penny & Feather
PIRA: 1C20.10
Description: A feather and a penny are placed in the tube which is “capped” on both ends. When the tube is held vertically the penny will fall faster than the feather. The tube is fitted with a valve and can be evacuated using the vacuum pump. When the tube is evacuated, the penny and feather will fall at the same rate.
Inclined Air Track
PIRA: 1C20.30
Description: The track can be used to demonstrate various things. In conjunction with the motion sensor x(t), v(t), and a(t) can be shown.
Fan Cart
PIRA: 1C20.31
Description: This cart has a permanently attached fan. When it is turned on, the cart demonstrates constant acceleration.
Various Balls
PIRA: 1C20.40
Description: A number of different balls can be dropped to show constant acceleration. (Basketball, tennis ball, racquet ball, ping pong ball, medicine ball, styrofoam ball, various metal balls bouncy balls)
Law of Falling Bodies {moon, Mech. Univ. video}
PIRA: 1C20.46
Description: Mechanical Universe video clip showing the simultaneous dropping of a hammer and feather on the moon. Full 28 minute Episode or Short clip on USB.
Motion in Two Dimensions
Plexiglas ring (cut and uncut) with a marble
PIRA: 1D10.45
Description: A Plexiglas ring has a segment cut out of it. When marbles are rolled along the inside of the ring, they are shown to exit the ring in a straight line, traveling tangentially to the ring. This is similar to the Ball on a String.
Ball on a String
PIRA: 1D50.10
Description: Tie a lightweight ball to a sting and twirl around in a vertical circle.
Bucket of Water or Wine Glass
PIRA: 1D50.40
Description: A bucket partially filled with water can be swung in a vertical circle with a radius of arm’s length. If swung with the appropriate speed, the water will not spill. The bucket can also be attached to a rope and swung in a vertical circle. Practice before you try this one.
Simultaneous Fall
PIRA: 1D60.20
Description: The objective of this demonstration is to show that when an object has horizontal velocity, gravity is acting upon it in the same way that it acts upon a dropped object.
The top portion of the figure has a mechanical device that sends two balls in motion at the same time, one with no horizontal motion and one with horizontal motion.
The mechanical device is triggered and both balls begin their descent. These two balls will hit the aluminum sheet at the same time because they will still have the same vertical force acting upon them. The device projects one ball horizontally while simultaneously dropping a second ball vertically; both balls land at the same time illustrating that the horizontal motion of the one ball does not affect its vertical motion at all.
Monkey Hunter
PIRA: 1D60.30
Description: Illustrates that a projectile fired at some initial angle with respect to horizontal falls at the same rate as the monkey falling vertically, so that the “hunter” should always aim at the monkey to make a hit. A stuffed monkey is hung from an electromagnet powered by the Lab volt supply or GW Power Supply (16-18 VDC).
The magnet is turned off when the dart exits the barrel of the air gun. The dart and the monkey are in free fall simultaneously. If the dart is aimed directly at the monkey, the dart should strike the monkey as it falls. If the gun is pumped 2 times, the velocity of the dart will be small and the collision will occur near the floor. If the gun is pumped 4 times, the velocity of the dart is large and the collision will occur nearer the point of release.
The monkey can be suspended from a 2 meter pole set on top of the demonstration bench (~3 meters off floor). The monkey must be hung from the plunger which extends from the electromagnet. When the magnet is turned on, the plunger is drawn in and the monkey slips off. Once the projectile is launched, either it must be returned to the gun or the power supply must be shut off otherwise the continuous current will damage the electromagnet.
Pop-up Cart
PIRA: 1D60.32A cart is pushed along on a dynamics track and launches a ball vertically when it passes through a switch. The ball makes a parabolic path through the air and lands back in the cart.
Juggling Balls or Flaming Torches
PIRA: 1D60.61
Description: For the instructor who is able to juggle, we have Torches or balls.
Relative Motion
Crossing the River (Digital)
PIRA: 1E10.10
Description The relative motion of a boat on a river. The motion of the boat is added to the motion of the river current, and the sum of the vectors is viewed from an overhead camera. (Old Cinema Classics Video on USB)
Newton’s First Law
Inertia Ball
PIRA: 1F20.10
Description: A mass is rigged with 2 eye screws at opposite points and suspended with a piece of string and an identical piece of string is hung from the bottom of the mass. Pulling on the lower string slowly breaks the upper string first. Jerking on the lower string breaks the lower string first. The inertia of the mass keeps it from moving quickly.
Tablecloth Pull
PIRA: 1F20.30
Description: A full table setting (table cloth, plate, flatware, candle, champagne bottle, saucer, and cup) can be set on the table cloth. With a little practice, the table cloth can be pulled from under the setting. There are no hems on the table cloth. It is best to pull slightly downward over the edge of the table as you pull out. The tablecloth is jerked away without disturbing the place setting illustrating the concept of inertia.
Pencil Drop
PIRA: 1F30.50
Description: A short pencil is placed on top of a narrow vertical hoop which is resting on the opening to a pop bottle. When the hoop is removed sufficiently fast, the pencil falls into the bottle.
Newton’s Second Law
Smart Pulley, Cart, Masses and Dynamics Track
PIRA: 1G10.10
Description: Masses can be used to pull the cart via a string over the smart pulley. The velocity and acceleration can be displayed.
Block on Incline Plane
PIRA: 1G10.25
Description: Accelerate a block of wood across a table by a mass on a string over a pulley.
Force Sensor – mass (vertical)
PIRA: 1G10.36
Atwood’s Machine
PIRA: 1G10.40
Description: This Atwood machine is constructed with a large pulley supported form a 2-meter rod. With 1 kg mass hangers suspended form each side, the system stays in equilibrium. At least 50 g is necessary to accelerate the system. The moment of inertia of the pulley has not been measured.
The pulley weighs 2.835 kg.
Statics of Rigid Bodies
Map of State
PIRA: 1J10.10
Description: The center of mass of a state of Washington map can be found by using an arrow shaped plum bob and drawing a couple of lines. Three different holes near the maps edge are capable of supporting the map so it will hang vertically. The three points on the map are Pullman, Cougar Island, and Cougar. Center of mass is near Blewett Pass. Hang the map on a nail (provided) with the arrow plum bob on top of the map. Draw a line. Repeat for one of the other holes in the map. The center of mass is located at the intersection of the lines.
Leaning Tower of Pisa
PIRA: 1J11.10
Description: A model of a tower is made in two pieces. The bottom piece is stable. When the top piece is added, the center of mass is shifted outside the base of the tower and the tower tips.
Balancing Bird
PIRA: 1J11.12
Double Cone
PIRA: 1J11.50
Description: As a double cone moves up a set of inclined rails, its center of gravity lowers.
Duck on a Rope
PIRA: 1J30.11
Description: A mass hangs below the rope and the duck balances above the rope. No matter how hard you pull on the ends of the rope, you cannot bring the duck up to the level of the rope ends. Near the center of a segment of rope, sits a duck with a mass attached below the duck. No matter how hard you pull on the ends of the rope, the duck cannot be lifted to the level of the rope ends.
100 cm. Balance Beam
PIRA: 1J40.22
Description: A beam, pivoted through its center of mass, has support hooks distributed evenly along its length. If a mass of, say, 200 g is hung at the 5 mark on one side, it can be shown to balance with a mass of 500 g hung at the 2 mark on the opposite side. The beam is supported by a clamp and support rod.
Torque Beam
PIRA: 1J40.40
Applications of Newton’s Laws
Tipping Block
PIRA: 1K10.10
Description: Pull with a force sensor at various angles on the edge of a block to see the least amount of force required to tip the block.
Slipping Ladder
PIRA: 1K10.20
Description: A model ladder is placed against a box and a weight is moved up one rung at a time. Eventually the center of mass is reached and the ladder begins to slip.
Break the Bolt
PIRA: 1K10.22
Description: Half-inch bolts can be broken in half, given enough torque. A thick plate of aluminum has tapped holes through most of its depth but they do not go all the way through. When a bolt is started down the hole, it gets to the bottom and will no longer turn. A “breaker bar” socket handle with a 3/4″ socket along with a long metal tube slipped over the handle will easily break the bolt in half.
Returning Coffee Can
PIRA: 1K10.43
Description: The coffee can is loaded with a rubber band and a lead weight. When the can rolls forward, energy is stored in the twisted rubber band. This stored energy is then returned as the can rolls back.
Styrofoam Model
PIRA: 1K20.06
Description: Thin sheets of Styrofoam can be carved to a wedge using a razor blade. The shaved edge reveals a jagged uneven edge. If two such wedges are place on the overhead projector, there shadows display a model of magnified surfaces to help explain the phenomenon of friction.
Block on an Incline
PIRA: 1K20.12
Description: Used for various demonstrations. Usually it is used with a protractor to measure the incline at which the block begins to slide. {the point where it breaks static friction}
Rotating Table
PIRA: 1K20.13
Description: A block rests on a turntable and the string goes to a dynamometer. The table accelerates to the point that the block slides off the table.
Sandpaper Block on an Incline
PIRA: 1K20.14
Description: The massive block with different grit sand papers on the surfaces can be used to explain frictional forces. If used in combination with an inclined plane, the coefficient of static friction can be obtained. Bricks can be used in the same fashion.
Area and Weight Dependence of Friction (bricks)
PIRA: 1K20.15
Description: Bricks can be pulled along a surface using a force sensor to measure the force. Some force exists before the bricks begin to move. The bricks are tied together in such a way that the surface area can be doubled or the mass can be doubled and the surface area can be reduced.
Pull Block with Fish Line {earthquake demo}
PIRA: 1K20.31
Description: A long string is attached to a large number of rubber bands that are hooked together and attached to a block that rests on the ground. The string is then attached to a dowel on a drill. As the dowel spins, the string wraps around the dowel until the tension on the rubber bands is great enough to pull the block forward. As tension overcomes friction, the block jerks forward. This happens repeatedly.
Pull Stacked Blocks
PIRA: 1K20.32
Description: A block with a string attached is placed on top of another block. If the mass of the top block is great enough, it will pull the bottom block with it when the string is pulled.
Truck with Locked Wheels
PIRA: 1K20.40
Description: Truck on which the wheels lock, demonstrates the idea that if a set of wheels on a vehicle are locked, the front wheels are preferred.
Bed of Nails
PIRA: 1K30.10
Description: Dr. Fred Gittes lies on the “Bed of Nails” YouTube video.
Gravity
Cavendish Balance
PIRA: 1L10.30
Description: Standard Cavendish experiment with lead balls and optical lever detection. (Not operational)
Energy Ball
PIRA: 1L20.05
Description: A tube has a cord passing through that is attached to a ball on one end and a mass on the other. While holding the tube vertically, the ball is swung in a circle fast enough so that the tension in the string supports the mass. The ball must be spun at a particular rate to balance the mass at the other end. This can simulate orbits.
Orbit Model (Orrery)
PIRA: 1L20.06
Description: Model displays the rotation of the moon about the earth and the earth about the sun. The model can also be used for discussions of eclipses.
Gravity Well
PIRA: 1L20.11
Description: The motion of an object “falling” into a gravity well can be displayed.
Work & Energy
Pulley System
PIRA: 1M20.11
Description: Single and Double Pulley systems. Place a mass on a string over a pulley and hold a spring scale at the other side. Repeat with a mass hanging from a single pulley in a loop of string.
Bowling Ball / Simple Pendulum
PIRA: 1M40.10
Description: When work is done in pushing the bowling ball or pendulum to the side, gravitational potential energy is stored. When released, the potential energy is converted to kinetic energy via the work done by gravity. To show conservation of energy, the instructor can position the ball or pendulum in front of his face and then release it from rest. On the return swing, the instructor will not be hit since extra energy cannot be added to the system.
Impact Pendulum/ Newton’s Cradle
PIRA: 1M40.12
Description: Five large steel balls with bifilar suspension are arranged so that they hang just touching each other while at rest. When one ball is raised and allowed to swing toward the others then, after the collision, one ball will rise on the opposite side. If two balls are raised, then two balls exit.
Conservation of energy and momentum can be discussed.
Loop the Loop
PIRA: 1M40.20
Description: The objective of this demonstration is to show approximately the minimum height at which the ball can be dropped so that it will make it all of the way around the loop.
Demonstrate that if the ball is dropped from the position parallel to the top of the loop then when the ball gets to the top of the loop it does not have enough velocity to carry it around the loop and will just fall. Describe to the students that there must be enough velocity.
Roller Coaster
PIRA: 1M40.35
Description: This roller coaster can be used to talk about conservation of energy and loss of energy. On a short time scale, potential energy is converted to kinetic energy and vice versa. For a longer time, energy is obvious lost from the system to sound and friction, etc. The ball will eventually come to rest.
Ballistic Pendulum
PIRA: 1M40.40
Spring & Mass
PIRA: 1M40.62
Description: Demonstrates that the spring stretches when force is applied to the string.
Spring & Force Sensor
PIRA: 1M40.63
Description: Demonstrates that the spring stretches when force is applied to the string.
Bathroom scale & timer {run up steps, h=2.6 m}
PIRA: 1M50.30
Description: A student runs up the stairs of B16, having had their weight measured, and their run is timed. With this information, the work performed by the student can be determined.
Linear Momentum & Collisions
Spring Apart Air Track Gliders
PIRA: 1N20.20
Description: Burn a string holding a compressed spring between two air gliders with different mass.
Floor Cart and Medicine Ball
PIRA: 1N21.10
Description: Two people on roller carts throw a medicine ball to each other.
Water Rocket
PIRA: 1N22.20
Description: A toy rocket with a pump can be filled with either air or water. The air in the rocket can be compressed with the pump. With only air, the change in momentum of the rocket is small since the mass of the air is small. With both air and water, the change in momentum of the rocket is large since the mass of the escaping water is large.
Basketball & Racquet Ball
PIRA: 1N30.10
Description: The balls are placed on top of each other and dropped form shoulder height to demonstrate the transfer of momentum.
Air Track Collisions
PIRA: 1N30.30
Description: The transfer of momentum is demonstrated using the air track. Air track gliders can show all combinations of linear collisions. Elastic and inelastic collisions with equal and unequal mass gliders can be clearly exhibited on a near frictionless surface. Springs are attached to the gliders on one end and a small amount of clay on the other produce the elastic and inelastic conditions.
Rotational Dynamics
Inertia Wands
PIRA: 1Q10.10
Description: These particular wands can be used to observe the rotational motion of an object relative to its center of mass. One wand is weighted in the center, the other wand is weighted at each end.
Ring, Disc, and Sphere
PIRA: 1Q10.30
Description: A disk, a hoop, and a sphere will have different accelerations dependent on their moment of inertia as they roll without slipping down an incline. Roll them down an inclined plane to see which one reaches bottom first. The students can be asked to predict which object will reach the bottom of the incline first. The disk and hoop are designed to have the same mass and radius to show that the acceleration is independent of these two quantities.
Angular Acceleration Apparatus
PIRA: 1Q20.20
Description: The apparatus consists of a pulley, a rod centered on the pulley, and two masses which slide along the rod. The masses can be clamped at any position on opposite sides of the center of the rod. If the masses are clamped at the end of the rod, the moment of inertia of the system is large and, when a constant torque is applied, the angular acceleration will be small. If the masses are clamped near the center of the rod, the moment of inertia of the system is small and, when a constant torque is applied, the angular acceleration will be large. The constant torque is provided by a rope wrapped around the pulley and attached to an unsupported 100 g mass. The system is supported by a support rod and clamp.
Falling Wine Glass on a String
PIRA: 1Q20.28
Description: A string is tied to the base of a wine glass and has a small mass on the other end. The string is then placed over a rod with the glass hanging down one side and the small mass is held horizontally on the other. When the mass is dropped, the string wraps around the rod and the glass does not hit the floor.
Falling Meter Stick
PIRA: 1Q20.56
Description: Blocks rest on a meter stick held up horizontally from a pivot point. When the meter stick is allowed to fall from the pivot point, the blocks closest to the pivot point remain closest to the meter stick.
Weights Dropped on Rotating Stool
PIRA: 1Q30.31
Description: Demonstrates the conservation of angular momentum. The stool is first spun, and then weights are dropped on top of the stool. When the weight is added, the stool spins more slowly.
Rotating Stool with Weights
PIRA: 1Q40.10
Description: Conservation of angular momentum can be demonstrated with a low friction bar stool. The instructor or a student when spinning on the bar stool has a vertically oriented angular momentum vector. The person on the stool can change their moment of inertia by extending or pulling in their arms and legs (extra weights can be used). By changing their moment of inertia in the absence of external torques, their angular velocity will change oppositely. The bike wheel can also be used to show angular momentum conservation. The change is angular velocity of the person on the stool will be greatest when the wheel axis is vertical and the axis is then rotated 180 degrees.
Governor
PIRA: 1Q40.23
Description: This shows the increase in angular speed when the weights are moved toward the axis of rotation. The device will rotate at about the same speed when allowed to spin freely due to the weights.
Rotating Stool with Bike Wheel
PIRA: 1Q40.30
Description: This demonstrates rotational inertia and torque. When the stool is stationary, the bike wheel is spun vertically and moved to a horizontal position. As the wheel changes from vertical to horizontal, the stool turns as well.
Bike Wheel Gyro
PIRA: 1Q50.20
Description: A bike wheel can be hung from its axle by a cable. When the wheel is spinning, the axle will stay horizontal and the wheel will precess.
MITAC Gyro
PIRA: 1Q50.30
Description: If the gyroscope is placed on a cart which can be moved about, it can be shown that the gyro will always point in one direction. A pennant can represent the compass reference used onboard ships. Precession can be shown by placing a weight on one end of the axis arrow.
Air Gyro
PIRA: 1Q50.45
Description: A large steel ball with a rod running through it can have weight added to the rod. Precession can be shown
Tippe Top
PIRA: 1Q60.30
Description: A toy top when spun inverts itself so that it is top heavy.
Energy Ball
PIRA: 1Q60.52
Description: A tube has a cord passing through that is attached to a ball on one end and a mass on the other. While holding the tube vertically, the ball is swung in a circle fast enough so that the tension in the string supports the mass.
Break the Bolt
PIRA: 1Q70.10
Description: Half-inch bolts can be broken in half, given enough torque. A thick plate of aluminum has tapped holes through most of its depth but they do not go all the way through. When a bolt is started down the hole, it gets to the bottom and will no longer turn. A “breaker bar” socket handle with a 3/4″ socket along with a long metal tube slipped over the handle will easily break the bolt in half.
Properties of Matter
Stretch Springs
PIRA: 1R10.10
Description: This demonstration is designed to introduce Hooke’s law and show how to calculate the spring constant. A mass is hung from a string. The spring’s length is measured. It is then stretched out and remeasured. The formula for the force of the spring is introduced, FSpring = -kx. The force being exerted on the string is the weight of the object = mg. So, mg = -kx. K can be found by dividing mg by the amount that the spring was stretched.
Foam Stress
PIRA: 1R30.20
Description: Push on the top of a large foam block to show shear.
Bouncing Balls
PIRA: 1R40.10
Description: Different composition balls are dropped down a Plexiglas tube to measure their rebound. The balls impact a steel anvil and the height to which they rebound is marked with rubber bands on the glass tube. The coefficient of restitution is determined.
Live and Dead Balls
PIRA: 1R40.30
Description: Similar looking balls are dropped onto an anvil. One will bounce and the other will not bounce at all.
Various Crystal Model
PIRA: 1R50.20
Description: Ball and stick lattice models of NaCl, sodium carbonate, graphite and diamond.