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Defying Gravity? Hardly

Guest Elliott56


Based on what we have just learned about torque and rotational motion, should this be possible? I understand the fact that the two objects, equal in weight, would not twist the system around the toothpick, thus maintaining the rotational static equilibrium in this direction, but it is the other direction that astounds me. The fork and spoon are hanging out away from the glass and i would thus expect it necessary for a countering force to be applied on the opposite side of the pivot. When all mass was burned up from the other side i figured the system must fall off of the cup, but instead it remained in equilibrium. I could not think of a reason why this would be, so i decided to set up the experiment myself. I did exactly what was done in the video and found that my forks too stayed up after burning the one end of the toothpick. So what could be the reason why the masses don't tip over? After thinking about it a while longer, i determined that the center of mass of the two forks as one unit lies not anywhere on the forks themselves, but somewhere between the two handles. By adding the toothpick, this location of the center of mass will fall on the toothpick and thus the system itself. As we have learned, an object will be perfectly balanced when held at its center of mass and thus when this point is placed on the cup, there will be no torque in any direction for it is the equivalent of holding a disk at its center, the center of mass.

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