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# Viscosity and fluids watch

1. In an experiment a small metal ball is dropped into a cylinder of oil. The time taken forthe ball to fall to the bottom of the cylinder is recorded.

The experiment is repeated. Which changes to the ball would result in the greatestdecrease in the time it takes to reach the bottom of the cylinder?
A smaller mass and smaller diameter
B smaller mass and greater diameter
C greater mass and smaller diameter
D greater mass and greater diameter

The answer is C, why? my textbook says "the drag force isdirectly proportional to the radius of the sphere, anddirectly proportional to the velocity" and also "doubling the ball’sradius makes its terminal velocity four times as great.". It also says larger objects fall faster

doesnt that mean that making the diameter bigger means increasing velocity (speed at which it will reach bottom will be fast). can someone please explain this? thank you

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Updated: November 6, 2015
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