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Old Apr 12th 2017, 05:56 AM   #1
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question about the force of an object hitting another

if you have scenario A)a flat square or flat circular object, and it moves in a straight line, towards an object e.g. a ball. vs B)A flat square or flat circular object, moves in a straight line towards an object e.g. a ball (so same so far), but also, the flat object is spinning in the Y axis too, and the centre of the spinning flat object hits the ball. So the ball still goes straight. Will the ball go faster or slower or same speed, in A, or B?
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Old Apr 12th 2017, 08:12 AM   #2
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Instead of using terms like "flat circular object," can we simply say it's a baseball bat? And how do you define the "Y axis?" Is it aligned with the center line of the barrel of the bat (for example the barrel of the bat rotates as the batter's hands turn over in mid-swing)? If that's what you mean, then the rotation has no effect on the linear velocity of the ball coming off the bat, but the spin that's induced in the ball may help it travel farther through the air (similar to how the spin on a fast ball causes it to seem to "rise" compared to a sinker ball).
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Old Apr 12th 2017, 08:28 AM   #3
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oh I meant circular and flat, like a plate.

this video may help




thanks
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Old Apr 12th 2017, 09:06 AM   #4
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The video helps. The spin of the book makes no difference to the resulting speed of the ball, assuming the object (your book) hits the ball exactly at the center of rotation of that spin. In other words the book is spinning about the y-axis (to use your term from before), and if the ball contacts the book at a point that's on that axis, the spin of the book has no effect. The reason is that the velocity of the book's contact point is the same in both scenarios.
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Old Apr 24th 2017, 04:36 AM   #5
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Thanks

btw, not sure if the forum appreciates somebody posting thanks, or if it is seen as white noise?
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Old Apr 24th 2017, 10:59 AM   #6
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We're always happy to receive positive reinforcement! Thank you!
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