In a normal pocket shot for a RH bowler, the headpin hits the 2-pin and goes toward the left wall. The ball takes out the 1>3>5>9 pins.
On a solid 8-pin, the headpin spins and deflects off the 2-pin straight back (into the 5) instead of to the left toward the wall. The ball takes out the 1>3>9. Missing the 5-pin means the 5 cannot be driven into the 8-pin.
It's a tough break.
The 9-pin leave is ususally caused by too much entry angle, and the ball has too much momentum/drive to deflect back to the right toward the 9, thus passing just left of the 9-pin.
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Dan
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Engineering * Bowling = a fun and practical application of rotational kinematics.
Bowling Nerd Herd (TM) Member