How much does the tip deform during contact with the cue ball?
Here’s an image from some high-speed video filmed by a group from Austria:
The full video clip can be viewed at HSV A.76 (it is the third clip in the sequence). The video was shot at 2000 frames per sec with a high-resolution color camera. Here’s an isolated clip of the close-up of the tip contact:
I’ve collected a sequence of images from the video clip and have made them available in MS Word and PDF formats. The MS Word file is large (1.7 MB), but it is very useful. If you page down through the file to load all of the images, you can then use the scroll bar to simulate a flip-book animation. The faster you scroll, the faster the simulated “video” plays. The images are 1/2000 second (0.0005 or 5 ten-thousandths of a second) apart.
Here are some observations, insights, and questions from the collection of stills:
– The tip is probably relatively soft based on the contact time and amount of deformation. Contact lasts about 4 frames (over frames 3-6), which corresponds to about two thousandths (0.002) of a second.
– The cue tip seems to stay in contact with the ball as the ball starts to rotate, which might contribute to the amount of cue stick deflection.
– The cue tip had an excessive amount of chalk on it (as evidenced by the pre-impact chalk trail through the air and by the huge chalk cloud after impact).
Here’s another excellent video showing the tip dynamics during contact:
Here’s another video comparing tip compression for various tip hardnesses:
See also: TP B.22 – How peak tip contact force and contact patch size vary with shot speed, and drop tests.
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