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Statics of Rigid Bodies

  • C6-03: INCLINED PLANE - FRICTION WITH THREE BLOCKS

    C6-03
    Illustrate different coefficients of friction.
    As the inclined plane angle is steadily increased, the three blocks begin to slide in the following order: (1) teflon, (2) styrofoam, and (3) rubber.
    C6

  • D2-04: MOMENT OF INERTIA RODS

    D2-04
    Demonstrate dynamic effects of the center of mass and moment of inertia

    Four rods are included: The first set (taken from the demonstration B1-17: CENTER OF MASS - STICKS) includes a uniform wooden rod and a second rod with a weight at one end. The second set are two rods with the same mass, one weighted at the center and one weighted at both ends.

    The student is asked to determine the difference between the rods. The difference between the first set is readily apparent, but determining the difference between the second set requires some experimenting. One way to "feel" the difference between the two latter rods is to hold each at the center and rotate your wrist back and forth. The large moment of inertia of the rod with weighted ends makes rotation of your wrist rather difficult compared with the rod weighted at the center.
    B1, D2

  • D2-05: DUMBBELL - VARIABLE MOMENT OF INERTIA

    D2-05
    Demonstrate the effect of moment of inertia.
    Hold the dumbbell at its center and rotate it rapidly in alternating directions. Then change the moment of inertia by sliding the weights along the rod. See how moment of inertia affects the speed and effort with which you can change rotation.
    D2

    d2-05a

  • F2-25: BALANCE PARADOX - BUOYANCY WITH CROSSOVER

    F2-25
    Present buoyancy in a paradoxical way.
    The balance is initially at equilibrium with a mass hanging from an arm on the left pan in balance with the water beaker on the right pan, as seen in the photograph at the left above. Q: If the mass is allowed to hang into the beaker of water, how does this effect the balance? In particular, what, if anything must be done to restore equilibrium? (Note that there are a 100 gram weight and two 50 gram weights available at the lower left of th picture, and these weights can be added to either side of the balance to restore equilibrium.) A: Because the volume of the block is 50 cm^3, the weight on the left side is reduced by 50 grams when the block is submerged in the water. Conversely, the weight on the right side is increased by 50 grams, the reaction force on that pan. To restore equilibrium, 100 grams must be added to the left pan, as seen in the photograph at the right above.

    f2-25a