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12-07-2002, 02:20 PM
Hi, I have an interesting physics question for you to ponder. There is a board lying on its side on an ice rink that is completely frictionless (this all takes place in 2 dimensions). The length of the board is about three times its width. There are three different experiments with this board. In the first experiment, a force of magnitude F that is applied at the very end of the board at an angle exactly perpendicular to the side of the board. In the second experiment, the force F is applied to the board at a location halfway between the end of the board and the center of its mass (which is in the middle of the board). In a third experiment, the force is applied directly in line with the center of mass. In the three different experiments, the magnitude and direction of the force is the same. In class, we are studying torque and angular movement, so the answer has something to do with these subjects. The BIG question: Of the three blocks, which block's center of mass accelerates (transnational acceleration, not angular acceleration) the fastest? My teacher claims that the acceleration is the same in each case, but I do not think that is right. Could someone help me understand this? I will most likely need a mathematical, not intuitive explanation to fully understand what is going on in this experiment. Thanks!!

12-10-2002, 04:12 PM
funny, sounds just like this:


i have no idea if my math and physics are correct though.

12-28-2002, 01:11 AM
Any force that is applied at a distance d from the CG can be replaced by two components: the force itself, applied through the CG, and a rotational component, resulting from the force, that is equal to force x distance, d. Using this approach, the force will always be acting through the CG and since frictionless with no concern for rotation, the board will always accelerate and translate the same. :D


12-29-2002, 11:26 PM
OMG everytime i go to read in this forum its all

The force of friction time mass multiplied by the x postion of the indirect conventional energy loss results in a forward motion provided by the exomagnetic polarity of the motion trail.

How the heck am i ever gunna learn. Got any good books?
Sorry whats CG? Cross gravity? conventional gravity? Corresponding gravity? Correct gravity? I really wanna learn this stuff. But i am stupid 12 year old.