An umbrella tends to move upwards on a windy day principally because
A)trapped air under the umbrella, warms, and rises.
B)buoyancy increases with increasing wind speed.
C)air pressure is reduced over the curved top surface.
D)all of the above

Question

Quizplus · Accepted Answer

The curved top surface of the umbrella reduces air pressure on the top, creating a reduced pressure area. The air below the umbrella has a higher pressure which causes the umbrella to move upwards. Option A is incorrect as trapped air does not warm up to a level that would cause buoyancy to overcome the downward force of gravity. Option B is also incorrect as buoyancy is not affected by wind speed, but by the difference in pressure between the displaced fluid and the object.

An Umbrella Tends to Move Upwards on a Windy Day