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Properties of Matter

  • A1-03: DENSITY - VARIOUS BRICKS

    A1-03
    Demonstrate the concept of density
    This demonstration consists of several bricks of approximately the standard "brick" size and shape, made of various materials such as foam, concrete, steel, and lead. Because the sizes are similar and the weights different, the feature creating the difference must be the density, or mass per unit volume. Invite students to make predictions about which will be heavier, then come up to pick them up and test their predictions.
    OS6

  • B4-01 HOOKE'S LAW

    B4-01
    Demonstrate the linear relationship between force and stretching for a simple spring.
    Two weights are provided to show linearity over a factor of two in applied force.
    FS2

  • B4-02: HOOKE'S LAW - COMPRESSING A SPRING

    B4-02
    Demonstrate Hooke's law for a spring under compression.

    This tabletop demonstrations illustrates Hooke's Law in compression, for comparison to the typical hanging-spring examples. Add weights to observe that the compression of the spring is approximately proportional to the amount of weight added.
    FS2

  • B4-11: ELASTIC LIMIT OF RUBBER BAND

    B4-11
    Demonstrate Hooke's law and elastic limit.
    Load small weights to demonstrate Hooke's law. Hanging a few kilograms from the rubber band exceeds its elastic limit.
    FS2, ME1

    b4-11a

  • B4-12: ELASTIC LIMIT OF SOLDER SPRING

    B4-12
    Demonstrate the elastic limit for an inherently inelastic object.
    Place spring on overhead projector, and stretch and compress it. It will quickly become obvious when the elastic limit is exceeded.
    B4

  • B4-13: ELASTIC LIMIT OF A BALLOON

    B4-13
    Burst a balloon.
    Connect balloon to air compressor and blow up the balloon. The picture at the right shows how to connect the balloon to the compressor using a rubber cork and an o-ring.
    B4, I0

    b4-13a

  • B4-14: ELASTIC LIMIT OF WIRE

    B4-14
    Demonstrate the variation in tensile strength with wire diameter.
    Two wires are used: 24 AWG, 0.474 mm diameter, and 20 AWG, 0.786 mm diameter. The ratio of tension required to break two wires is proportional to the square of their diameters, for this case F2 / F1 = 2.75. The two wires can be broken, the required tensions read off the attached spring scale, and the ratio calculated.
    B4

  • B4-31: FAILURE OF WOOD IN COMPRESSION

    B4-31
    Demonstrate the dependence of the compressional strength of wooden dowels on their diameter and length.
    Place dowel vertically between the plates of the hydraulic press, and compress dowel until it collapses. A 5/8" dowel requires about 1.0 tons, a 7/8" dowel about 2.2 tons.
    B4, FS1

    b4-31a

  • B4-33: EGG CRUSHER

    B4-33
    Show that an egg can support unexpectedly high forces due to its curved shape.
    An egg is positioned vertically between the "egg crusher" base and top cylinder. The two surfaces are coated with heavy rubber discs to distribute the load. Up to 150 lbs of lead bricks (6 bricks) can be placed on the platform without breaking the egg, though no more than 4 bricks is usually recommended. The lower left photograph shows an egg in the crusher with 50 pounds of lead on it; the photograph at the right is a close-up of the egg in the center photo.

    Important note: Egg must be supplied by instructor.
    B4, FS1

    b4-33a b4-33b

  • C7-14: COLLISIONS OF BALLS WITH FLOOR

    C7-14
    Illustrate collisions of different balls with the floor.
    Drop the four balls simultaneously. They rebound to heights dependent upon the elasticity of the collisions with the floor.
    C7

  • C7-16: HAPPY AND UNHAPPY BALLS

    C7-16
    Illustrate coefficient of restitution.
    Drop the two balls simultaneously from the same height. One bounces back to almost the original height, while the other stops dead on impact. Which one is happy and which one is unhappy? The happy ball is made from neoprene rubber; the unhappy ball is made from norbornene, a polymer synthesized from ethylene cyclopentadiene.
    C7

  • C7-17 SUPERBALL

    C7-17
    Illustrates nearly elastic collisions
    Drop the superball and watch it bounce
    C7

  • C7-24: SILLY PUTTY

    C7-24
    Show collisions with an unusual material.
    Silly putty, being a non-Newtonian fluid, is malleable like clay, yet bounces like a ball.
    C7

  • C7-26: BOUNCING PUTTY AND NON-BOUNCING SUPERBALL

    C7-26
    Show unusual collisions.
    A superball dropped into a container of sand will not bounce. Conversely, a ball of putty dropped onto a foam rubber pad will bounce nicely.

  • C8-11 INTERNAL VS. EXTERNAL ENERGY - SPRING-COUPLED SUPERBALLS

    C8-11
    Shows that when energy disappears from the center of mass motion it may be converted into internal energy
    Hold the balls horizontally with the spring relaxed and drop; it should produce a high rebound. Then drop at an angle of about 45 degrees to the horizontal. The device will not rebound very high, but will develop a lot of internal energy, as evidenced by lots of spring vibration.

    This device can also be used as a simple model of energy in a two-atom molecule. Erik Neumann has created a simulation of this demonstration for this purpose as well. It can be found at https://www.myphysicslab.com/springs/molecule2-en.html .
    C8

  • C8-13: BUNGEE JUMPER MODEL

    C8-13
    Determine the minimum value of the spring constant of a bungee rope to ensure a safe jump.

    Student of mass M jumps from a cliff of height H tied to a bungee rope of unstretched length Lo. Assume a vertical jump with initial velocity of zero. Neglect air resistance and mass of the rope.

    When the spider jumps off the platform the spring extends to within a few inches (or centimeters in physics) of the floor before pulling the spider back up.

    DANGER - IMPORTANT NOTE: Bungee cords are made of shock cords (elastomers) or from rubber. They DO NOT behave as linear springs. It would be dangerous to assume linearity of a real bungee jumping cord and make calculations on this basis.
    FS1

    c8-13a

  • F1-11: HYDRAULIC PRESS

    F1-11
    Demonstrate dramatically Pascal's Law and the large forces attainable using hydraulic systems.
    Place the provided 2x4 board between the jaws of the press as shown in the photograph. Tighten the pressure release valve and pump the handle to increase the force and crush the 2x4. Pressure is read directly in tons. DO NOT exceed 5 tons.

  • F2-07: BUOYANCY - PEPSI AND DIET PEPSI

    F2-07
    Show the difference in density between soft drinks with and without sugar.
    Unopened cans of Pepsi and Diet Pepsi are floated in water. The Pepsi sinks, while the Diet Pepsi floats. The density of the Pepsi is increased by the dissolved sugar, which occupies space between the water molecules. Diet Pepsi has no additional sugar, and is therefore less dense.

  • F2-26: BUOYANCY PARADOX - BALL IN TWO LIQUIDS

    F2-26
    Demonstrate buoyancy with a counterintuitive element.
    A ball floats in a beaker of water (at left in picture above). The ball sinks in a beaker of mineral spirit paint thinner (at right above). The mineral spirit paint thinner is immiscible with water, and will float above the water when poured slowly on top of water. The ball then floats at a higher level because the mineral spirits in which the upper part of the ball is floating provide an additional buoyant force on the ball. If the ball is floating on water alone, the top part of the ball is immersed in air, which has a much smaller density.
    F2

    f2-26b

  • F2-31: BUOYANT BALLS IN BEANS

    F2-31
    Illustrate buoyancy in a surprising way.
    Begin with a heavy ball resting on dried beans in a bowl. Unbeknownst to the class, a ping pong ball has been placed under the surface of the beans. Shaking the bowl, the heavy ball sinks, while the ping pong ball rises to sit on the surface of the beans. Cover the bowl with a black cloth while shaking it, to make the whole thing more like a magic trick.
    F2, I6

    f2-31a