An umbrella has a tendency to move upward when it is windy principally because
1) moving air over the curved surface produces reduced pressure against its top.
2) air moves up into the "bowl" and pushes upward with increased pressure.
3) buoyancy increases with increasing wind speed.
4) the umbrella is simply pushed upward by the wind.
This effect was first accurately described by
5) Galileo.
6) Newton.
7) Bernoulli.
8) Einstein.
9) Archimedes.
Answer: 1, 7
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