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PHYS171

  • D4-03: BICYCLE WHEEL GYROSCOPE ON PIVOT

    D4-03
    Demonstrates gyroscopic precession and nutation
    Spin the bicycle wheel and release it with a small push to obtain pure precession, or release it without simultaneously pushing it to obtain precession with nutation. Release it with no spin to show that precession only occurs with the pre-condition of angular momentum of the wheel.

  • D5-01 TIPPE TOP

    D5-01
    Gyroscopic effect examples
    Start the top by spinning with the stem up and dropping it gently onto the table. As it spins, it begins to lean to the side then flips upside-down, rotating on its stem.
    D5

  • E1-11: POTENTIAL WELL -MODEL

    E1-11
    Demonstrates motion of planets or satellites in an inverse square gravitational field

    Giving a small ball a tangential velocity near the outer radius of the well, one can create elliptical orbits which demonstrate conservation of angular momentum as the ball rolls around the well.

    Invite students to predict how changing the ball’s starting velocity (in magnitude or direction) will affect its path. This is a good opportunity for one or more student volunteers to participate.

    Background

    The surface of this “potential well" is shaped so as to model an inverse square gravitational force. When a ball enters the well enters the well, it is attracted to the center; if it has no initial velocity, it will fall directly to the center. But if it enters with some velocity tangential to the center, it will fall into an elliptical orbit that gradually decays to the center as the ball rolls around the well.

    When you roll the ball across the surface, you use some initial force to start it moving. Once it is rolling on its own, though, the only forces acting on it are the force of gravity, pulling downwards, and the normal force and frictional force of the surface holding it up. So the ball accelerates as it rolls down the surface, exchanging potential energy for kinetic energy, until it falls into the hole.
    FS1, E1

  • F1-01 FLUID PRESSURE VS. DEPTH

    F1-01
    Demonstrates that fluid pressure increases linearly with depth and is isotropic.
    An L-shaped glass tube connected to a liquid manometer is inserted into a tank of water. The pressure in the water tank can be measured at any depth. Holding the tube at a particular depth and rotating it about the end will show no change in pressure, demonstrating that pressure is isotropic.
    F1, FS2

  • F1-06 WATER SEEKS ITS OWN LEVEL

    F1-06
    Shows that pressure is dependent on depth, not shape of container

    This set of conjoined glass tubes is filled with green-dyed water. The water level in the four different tubes is the same even though the volumes and shapes of the tubes are very different.

    Engagement Suggestion
    • For advanced students, consider tilting the tubes slightly, then plugging them with corks so that the different amounts of trapped air cause the water to be at different levels. Challenge students to analyze why this changes the results, then remove the corks to show what happens.
    Background

    This illustrates that the pressure in an open container of liquid is dependent only on the depth, not the shape or area.

  • F2-21 REACTION TO BUOYANT FORCE

    F2-21
    Demonstrates the reaction force using a liquid.
    A beaker of water is balanced by two brass weights. Stick your finger into the water about up to the first knuckle, the water side will go down. The water exerts a buoyant force on your finger, so your finger exerts a reaction to the buoyant force on the water, thereby causing the water side to go down.
    F2, ME1

  • F4-21: LIQUID IN SPINNING SPHERE

    F4-21
    Show the behavior of a liquid when subjected to a centripetal force.
    When the sphere is rotated, the water leaves the bottom of the sphere and forms a band in the middle of the sphere, due to the reaction to the centripetal force. Rotate sphere slowly to achieve this effect.
    F4, F1, D1

    f4-21a

  • F5-09 HAIRDRYER AND PING PONG BALL - COANDA EFFECT

    F5-09
    Illustrates levitation by an air stream
    Using the airstream from the hairdryer (with heater element disconnected), one can suspend a ping pong ball in the air. As the hairdryer is slowly moved or slightly tilted, the ball follows the airstream.
    F5

    F5-09A

  • F5-21 VENTURI TUBE WITH MANOMETERS

    F5-21
    Illustrates the venturi effect
    Turn on the blower and slowly move it so that it directs some air into the venturi tube device. The higher water level indicates less air pressure in that tube.

  • F5-22 VENTURI TUBE WITH PING PONG BALLS

    F5-22
    Illustrates the venturi effect.
    In this Venturi tube the levitation of the ping pong balls in an airstream is used as a pressure sensor; the higher the ball the greater the pressure of the air coming from that hole. Both the venturi effect and the reduction of pressure along the tube can be seen.

  • G3-28 SUSPENDED SLINKY

    G3-28
    Shows longitudinal and transverse traveling waves & standing waves
    Transverse or longitudinal pulses can be created by appropriate motion of your hand at one end of the SLINKY. Using your hand you can also create transverse standing waves and discuss the overtone series. Gently vibrating one end of the spring (either by hand or using the motor) at the appropriate frequency creates longitudinal standing waves.
    FS1

  • I1-11 THERMAL EXPANSION - BALL AND HOLE

    I1-11
    Illustrates thermal expansion
    At room temperature the ball will not fit through the hole in the metal plate. When the plate is heated by a burner for about 30 seconds, the ball easily fits through the hole
    I1, I0

  • I6-03 EQUIPARTITION OF ENERGY

    I6-03
    Demonstrates equipartition of energy
    Into the glass bowl are placed balls of the same size but three different masses: ping pong balls, cork balls, and superballs. Shaking the bowl gives all of the balls approximately the same kinetic energy. Because the light balls have greater velocities for the same average kinetic energy, as you shake the bowl more and more fervently first the ping pong balls, then the cork balls, and finally the superballs jump out.
    I6

  • I6-11: BROWNIAN MOTION WITH TV

    I6-11
    Demonstrate Brownian motion.
    A smoke cell is mounted on a tube connected to a TV camera. On the end of the tube inside the cell is a microscope lens which casts an image of smoke particles in the cell onto the videcon of the TV camera. The focal plane of the microscope/TV system is illuminated by a laser to avoid creation of convection currents by heating with a more powerful light source. A twisted lab tissue is burned and blown out, and while it is smoking the rubber bulb on top of the smoke cell is used to snort smoke into the cell through a tube in the bottom of the cell. After a few seconds convection ceases and Brownian motion is clearly visible on the TV monitor to large groups. The photographs above show the entire system (left), the laser beam entering the smoke cell which is in turn mounted on the video camera (center), and the output of the video camera sent directly to the video frame grabber used to capture the images (right). Clicking on the link below will play a 30 second MPEG movie of the particles in motion.

    i6-11i6-11ai6-11b

  • I6-23 DIFFUSION - FOOD COLOR IN WATER

    I6-23
    Demonstrates diffusion
    A drop of food coloring is placed gently into a beaker of water. In a few minutes the food coloring will diffuse through the entire beaker of water.
    F2, glassware

  • I6-26: DIFFUSION - PERFUME

    I6-26
    Illustrate diffusion.
    Spray the perfume into the air and the students soon notice the fragrance of the perfume. Point out that the perfume fragrance spreads through the room due to diffusion. Be sure to point out that there may be other reasons why the fragrance spreads, such as air currents.

  • P1-02: LOCAL INERTIAL FRAME OF REFERENCE

    P1-02
    Illustrates an inertial frame of reference

    A metal frame is suspended such that it can be held up by an electromagnet, and then drop freely onto a cushioned shock absorber. A pair of spring-powered cannon firing one-inch ball bearings are directly in line with holes in two plexiglass plates, one in the center and one on the side opposite the cannons. The second plate has sacks on the holes to collect the projectiles if they pass through the holes. Beneath the frame is a net to catch projectiles that do not go through the holes.
    Engagement Suggestion:
    • Before carrying out the experiment, encourage students to predict what will happen to the projectiles.
    • Will the level and angled cannon behave differently?
    • Once the students have seen it in action when at rest, have them make predictions again about what it will do in free fall.
    Background:

    If the frame is at rest, the projected balls fail to even go through the first set of holes because they are deflected by gravity. As they travel, they are pulled downwards, following parabolic paths with respect to the frame. If the frame is raised, held in place by an electromagnet and released, it falls with the acceleration of gravity and becomes a "local inertial frame of reference." The balls are automatically fired by a gravity switch when the frame begins to fall. The balls will travel along straight lines in the local inertial frame of reference and end up in the sacks before the frame stops on the shock absorber.
    FS0