- #1
Sefrez
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I have been messing around with a metal ruler, a slick surface, and a small flat head screw driver at which I have inserted into a plastic tube allowing me to connect a rubber band. It is basically a "pinball" launcher, if you will. I did this to create an impulse on the ruler at a high force over a little time interval to reduce effects of friction.
I know that when a force is applied to an object that no matter if there is a torque or not, the center of mass accelerates as if the force was applied there. But what about impulse between two bodies in an elastic collision? I figure the same stands, but the time and how the force is applied (I realize that in a collision this can be complex) must change depending on where the two bodies collide.
That is, doesn't a body that has translational motion only have less than that same body also having rotation motion? (E.g. k = 0.5mv^2 + 0.5Iw^2 > 0.5mv^2)
If that is true and it is true that the center of mass accelerates as if a force was applied directly to it - then that means a mass will have a total energy greater when a force also caused a torque upon it.
This makes sense in itself, but in an elastic collision where you have impulse (where forces may be more complex), it must be different as energy must be conserved. That is, if A object collides with the center of mass object B, B should translate greater than if it were to have been collided with its edge to conserve energy. Either that, or object A must retain more energy when colliding with the center of mass B to account for the rotational energy that B does not have.
Is this not correct?
Going back to my experiment with the ruler, I could not get any very accurate results, but I did seem to notice that the ruler translated about the same no matter where I hit it. The only thing that seemed to change much is angular rotation. My confusion if the results are valid? What I have just stated above and also what seems pretty clear to me - that the rubber band should have a quantifiable potential energy when pulled back to point x and thus the ruler should not have more total energy when hit at the edge. So my only assumption to this is that the amount of energy transfer between the two must vary depending on the point of contact. Is this correct?
I know that when a force is applied to an object that no matter if there is a torque or not, the center of mass accelerates as if the force was applied there. But what about impulse between two bodies in an elastic collision? I figure the same stands, but the time and how the force is applied (I realize that in a collision this can be complex) must change depending on where the two bodies collide.
That is, doesn't a body that has translational motion only have less than that same body also having rotation motion? (E.g. k = 0.5mv^2 + 0.5Iw^2 > 0.5mv^2)
If that is true and it is true that the center of mass accelerates as if a force was applied directly to it - then that means a mass will have a total energy greater when a force also caused a torque upon it.
This makes sense in itself, but in an elastic collision where you have impulse (where forces may be more complex), it must be different as energy must be conserved. That is, if A object collides with the center of mass object B, B should translate greater than if it were to have been collided with its edge to conserve energy. Either that, or object A must retain more energy when colliding with the center of mass B to account for the rotational energy that B does not have.
Is this not correct?
Going back to my experiment with the ruler, I could not get any very accurate results, but I did seem to notice that the ruler translated about the same no matter where I hit it. The only thing that seemed to change much is angular rotation. My confusion if the results are valid? What I have just stated above and also what seems pretty clear to me - that the rubber band should have a quantifiable potential energy when pulled back to point x and thus the ruler should not have more total energy when hit at the edge. So my only assumption to this is that the amount of energy transfer between the two must vary depending on the point of contact. Is this correct?
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