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Two identical lead pellets are released simultaneously into two glass jars, one containing water and the other glycerin. The pellet in glycerin sinks more slowly because

1. the viscous force is greater in water than in glycerin
2. the viscous force is greater in glycerin than in water
3. the surface tension of water is greater
4. the surface tension of glycerin is greater

Correct answer: the viscous force is greater in glycerin than in water

Solution

Glycerin is far more viscous than water, so the viscous drag on the falling pellet (proportional to viscosity by Stokes' law) is larger, giving a smaller terminal velocity and slower descent.

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