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Terminal velocity of a free falling object in a fluid is a frequent discussion topic for fluid dynamic/fluid mechanic engineers and others. What starts out as a relatively simple projectile problem can quickly become complex when real objects and drag become involved. Speed of sky divers, depth charges rolling off or shot off a destroyer (really complex because of tumbling etc).

Weight (actually density), size, shape, rotation, fluid properties are major variables. However, once we get practical (no tumbling or rotating flip flops allowed) and consider reasonably round, reasonably smooth (no dimples), small (I used 1 " diameter), somewhat dense(marble, stream gravel, metal beads, the fall distance for terminal velocity can be calculated (estimated).

My rusty analysis shows for round 1" stone, the terminal velocity is not reached until a fall of 250-300 ft, or more. It could be 500 ft for a smaller denser object depending on shape.

In one second an object would fall about 16 feet; 2 seconds a fall of 64 ft; 3 seconds 144 ft. Fall distance is a function of time squared. At 4 full seconds an object would fall about 260 ft and maybe approach terminal velocity.

Measuring time for short falls is easy in lab but tough in field. A small error for 16 ft is large; probably can get reasonable results for a 40 or 50 ft drop.
Could try to toss rock up a known height to a spar, and measure fall time from peak. Could drop a stone from a balcony into a barrel..... I will do none of these things because my GPS loving sons will be even more convinced that dear-ole-dad is misfiring on more than one cylinder.

I like dip arc minutes equals 4 times time seconds for 300 or more...as far as I can see.

Testing 1001-1002-1003...... Bruce
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