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  • B4-21: DEFLECTION OF BEAM - OPTICAL LEVER

    B4-21
    Demonstrate the small deflection of an aluminum beam due to weighting between supports.
    A mirror serves as an optical lever for the laser beam, with its fixed support legs on a lab jack and its other legs on the aluminum beam. The aluminum beam deflects as weights are added, causing the laser beam to move along the scale at the rear of the photograph.
    OS1, F1, ME1, LS1

    b4-21a b4-21b

  • 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

  • C1-03: CENTER OF MASS MOTION - CLOWN

    C1-03
    Illustrate rotation about the center of mass of an irregular object.
    The clown is suspended by strings wound on a peg located at the center of mass, which is outside the body of the clown. As the clown descends, it rotates about the center of mass.
    FS2

  • C1-04: CENTER OF MASS - BEAR ON TIGHT ROPE

    C1-04
    Show stability in system where the center of mass is outside of the object.
    As the bear rolls along the tightrope, it remains stable because its center of mass is below the rope. Removing the weights and poles renders the system unstable.

  • C1-11: AIR TRACK - CENTER OF MASS PENDULUM

    C1-11
    Show uniform motion of the center of mass of a vibrating pendulum/glider system.
    A symmetric (balanced) pendulum is suspended from an air track glider. The mass of the pendulum bob is approximately the same as that of the glider, so the center of mass (marked by a fluorescent disc) is approximately at the midpoint of the rod between the bob and the center of the glider. When the pendulum oscillates, the center of mass moves uniformly in the horizontal direction or remains motionless (horizontally).

  • C1-12: AIR TRACK - CENTER OF MASS OF COUPLED GLIDERS

    C1-12
    Demonstrate uniform motion of the center of mass of an oscillating system.
    As the gliders oscillate while moving along the air track, the center of mass (marked by an orange dot on the spring) moves with a constant velocity.

  • C1-13: AIR TRACK - REDUCED MASS

    C1-13
    Demonstrate the change in frequency for two-body oscillations.
    Two gliders are connected by a steel spring as shown in the photograph. With one mass taped down, the other mass vibrates with the standard period for simple harmonic motion: T = 2 pi sqrt (m/k), where k is the spring constant and m is the mass of the vibrating glider. If the two masses are pulled apart and released simultaneously, they vibrate out of phase with each other about the center of mass with a period T = 2 pi sqrt (u/k), where u = Mm/(M+m) is the reduced mass of the system. For M=m the reduced mass u = m/2, and the period is less by a factor of sqrt(2) = 1.414 than in the case of one glider oscillating.

  • C1-21: AIR TABLE - TOPPLING STICK

    C1-21
    Illustrate how a rigid rod topples on a frictionless surface.
    A wooden dowel with its center of mass marked is held vertically with the bottom end supported by a very light air table puck. When it is released and allowed to topple, which point of the stick will be directly above the original support point: the top end, the bottom end, or the center of mass? Note that the stick has a small counterweight on its top end to compensate for the mass of the puck. Click your mouse on the photograph for an mpeg video.
    FS0

  • C2-02: AIR TRACK - DIRECT MEASUREMENT OF ACCELERATION

    C2-02
    Measure acceleration using two different procedures

    All gliders are equipped with a 5 cm tab which interrupts the light beam when passing through the photocell gate. The timing system can be set to measure the time, ta or tb, a tab takes to move through the gate or the time, tab, taken for the glider to move from gate A to gate B (not B to A). The timer can be set at full scale ranges from 99.9 ms through 999 seconds for a range of applications.

    One timer is set so that it records the time for a glider to move from A to B. The second timer is set to measure the time the tab requires to move through gate A, and then after resetting, the time required for the tab to move through gate B. The acceleration, to an accuracy of less than about ten percent, can be computed using the equation:

    a = (v2-v1)/tab = mg/(M+m).

    where v1=5cm/ta and v2= 5cm/tb.

    Note: IMPORTANT NOTE: This demonstration uses BOTH photocell timing devices. You cannot do this demonstration and any other that uses photocell gates without major setup changes during class. We suggest that you do not request this demonstration for the same class as any other photocell timing demonstration.

  • C2-03: AIR TRACK - UNIFORM ACCELERATION - INCLINED

    C2-03
    Measure acceleration along an inclined air track.

    All gliders are equipped with a 5 cm tab which interrupts the light beam when passing through the photocell gate. The timing system can be set to measure the time, ta or tb, a tab takes to move through the gate or the time, tab, taken for the glider to move from gate A to gate B (not B to A). The timer can be set at full scale ranges from 99.9 ms through 999 seconds for a range of applications.

    One timer is set so that it records the time for a glider to move from A to B. The second timer is set to measure the time the tab requires to move through gate A, and then after resetting, the time required for the tab to move through gate B. The acceleration, to an accuracy of less than about ten percent, can be computed using the equation:

    a = (v2-v1)/tab = mg/(M+m). where v1=5cm/ta and v2= 5cm/tb.

    This can be compared with the component along the air track at the angle a: a = g sin a.

  • C2-04: FREE FALL WITH PHOTOCELL GATES

    C2-04
    Measure acceleration due to gravity
    The gates are set about x = 50 cm apart along the vertical line defined by the guide tube. A short aluminum cylinder is held immediately above the top photocell beam and released. The acceleration of gravity is then determined using the equation g = 2 x / t**2.
    C2, Ofc

  • C2-09: FREE FALL WITH STROBE

    C2-09
    Show the position of a dropped ball at a series of equal time intervals
    Drop the ball with the strobe on at the desired flash rate (about 10-13 flashes per second, or 600-800 per minute, seem to work well). The increasing distance the ball falls between successive strobe flashes is readily apparent.
    C2, FS1, LS1

  • C2-10: CONSTANT VELOCITY - GALILEO'S EXPERIMENT

    C2-10
    Show constant velocity and uniform acceleration using a rolling body.

    Rest the tube on the lecture table. Lift one end to obtain constant acceleration. Lift one end of the tube and immediately place it back on the table to obtain constant velocity.

    Rolling a sphere down a uniform incline led Galileo to some of the earliest conclusions regarding motion with a constant acceleration and to information regarding the acceleration of gravity on the earth.
    OS0

    c2-10a

  • C2-23: TRAJECTORY OF A BALL - MODEL

    C2-23
    Illustrate the position of a projectile at equal time intervals
    This apparatus is a model which shows the position of a projectile at equal time intervals after it is projected. The angle can be changed by tilting the meter stick from which the balls are suspended.

  • C2-24: WATER DROP PARABOLA

    C2-24
    Demonstrate the parabolic path of a projectile.
    A water stream is projected in front of a cartesian coordinate grid that can be shadow projected using a bright point source (not photographed). If desired, coordinates of the water stream can be read. The reservoir is a bottle which provides constant water pressure even as the water level drops in the container.
    C2, LS1

  • C2-51: KINEMATICS WITH ULTRASONIC RANGER

    C2-51
    Plot graphs of position, velocity, and acceleration

    The ultrasonic range detector is used with a computer to plot graphs of position, velocity, and acceleration. Linear motion can be created by a person walking along a line in front of the ultrasonic ranger. A large piece of styrofoam sheet can be used as a reflector for the ultrasound, to keep the curves as smooth as possible. Graphs of x, v, and a can be easily displayed individually or in any combination.

    The graphs of position and velocity are quite nice, but the acceleration can be a bit noisy, because it is obtained by differentiation of the position vs. time data. Try this before class.
    C2, FS1

  • C3-06: INERTIA: JENGA

    C3-06
    Demonstrate inertia of rest.
    This commercial toy consists of a stack of blocks with each layer placed 90 degrees to the prior one. The object of the game is to remove blocks from the lower part of the tower without knocking the whole structure over. Trying to do this gently is usually doomed to failure: a quick flick of the finger is the most effective method.
    C3

    c3-06a

  • C3-11: STRAW AND POTATO

    C3-11
    Illustrate inertia of motion

    If a plastic straw (like those from McDonald's) is pushed slowly into a raw potato, the rigid potato will cause the softer plastic straw to bend and break. However, if a significant velocity is given to the straw it can be pushed clean through the potato. This is what often happens in a tornado, where apparently softer objects are accelerated to high speeds by the wind and driven through apparently harder objects.

    Instructor must bring potato!
    C3

    c3-11a

  • C3-13 INERTIA: HAMMERHEAD

    C3-13
    Illustrates inertia in a hands-on manner
    A wooden hammerhead is loosely joined to a rigid plastic handle. It can move, with a great deal of frictional resistance. When the hammer is held upright and the handle struck sharply on the table, the head can be seen to move downwards along the handle, resisting the abrupt deceleration of striking the table. If the hammer is held in midair and shaken abruptly, the head can, with practice, be made to slide in either direction.

    Donated to the Facility by Tom Senior of the Physics Instructional Resource Association.
    C3

    c3 13b

  • C3-21: INERTIAL MASS CART

    C3-21
    Demonstrate the inertial property of mass

    Load the arms with equal masses at the same or different distances from the center, and observe what happens when the cart is accelerated by hand along the track. Alternatively, load the arms with masses in the ratio of 10:1 which look the same, and ask students to account for the behavior of the apparatus. By lifting one end of the track, show that when a force (gravity) is allowed to act uniformly on all parts of the apparatus the crossarm will not rotate regardless of how it is loaded.

    A simple demonstration sequence is to place more mass on one side (at front in pictures above) and accelerate the cart with your hand to illustrate inertial mass, then let the cart accelerate down the inclined track to illustrate gravitational mass.
    C3

    c3-21a