Lenski said:
NASCAR is NOT a sport
There have been a couple of mentions about centripetal force. Centripetal force is a kinematic force requirement, not a true force and does not apply to Newtons laws of motion. I believe the swing creates a centrifugal force (a kinetic force) which does apply to Newtons laws of motion (f=ma). Just before impact, the hitters body (reference frame) starts their hips, arms, hands, trunk, shoulders (axis of rotation) causing an outward force (centrifugal force). I might be wrong since I have not studied Dynamics in about 25 years....... :-/
Len
8. How to swing a bat (June 2008)
It is not difficult to swing a bat. It is almost as easy as walking. But how does a batter do it? Specifically, what forces and torques are exerted on the handle, and in what directions do they act? It is very surprising that noone seems to have worked this out before. Adair provides a few answers in his book ?The Physics of Baseball? but he does not give the directions or the torques. The diagram below shows the swing of a wood bat filmed from a spot above the batter?s head. The force on the bat can be worked out from the velocity of the center of mass, (CM), and the torques can be worked out from the angular acceleration. The results are very surprising. Initially, the force on the handle is in the opposite direction to the motion of the handle. While the center of mass moves one way (nearly upward here), the handle moves the opposite way (nearly downward). The batter needs to exert a small couple to get the swing started, using equal and opposite forces on the handle, otherwise the barrel of the bat will get left behind. Near the end of the swing, the force is roughly at right angles to motion of the handle since the centripetal force is very large. However, the centripetal force does not act along the axis of the bat, but at an angle, as shown by the orange lines.
The direction of the centripetal force is toward the center of the circle followed by the path of the CM. Since the CM traces out a spiral rather than a circular path, the center of the circle moves, as the bat is swung, along the path traced out by the inner circle of black dots. At any given time, the center of the circle can be found by fitting a circle to three neighboring points, at say time t, and at times t+0.02 s and t-0.02 s. This gives the radius, R, of the circle, from which we can calculate the centripetal force MV2/R as well as the force at right angles to that, given by MdV/dt.
Near the end of the swing, the batter needs to exert a large negative couple on the bat, otherwise the bat will swing around too fast and strike the ball when it is aligned at the wrong angle. The same thing happens when swinging a golf club, but it is not a well-known effect. Rather, most coaches and others think in terms of wrist torque, which is probably much too small to provide the necessary large couple near the end of the swing The couple must come mainly from the two arms, not the wrists.
http://www.physics.usyd.edu.au/~cross/baseball.html
Centripetal Force - The Real Force
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Whenever an object moves in a circular path we know the object is accelerating because the velocity is constantly changing direction. All accelerations are caused by a net force acting on an object. In the case of an object moving in a circular path, the net force is a special force called the centripetal force (not centrifugal!). Centripetal is Latin for "center seeking". So a centripetal force is a center seeking force which means that the force is always directed toward the center of the circle. Without this force, an object will simply continue moving in straight line motion.
http://www.regentsprep.org/Regents/physics/phys06/bcentrif/default.htm
Hope this helps....Howard