3 marksA group of students investigate the viscosity of a liquid. The group measured the force required to pull a small sphere upwards through the liquid at a constant speed.
The group measured the diameter of the sphere using a micrometer.
Calculate the percentage uncertainty in the diameter of the sphere shown on the micrometer.
1 markOutline one precaution that should be taken before using a micrometer.
5 marksThe group used a force gauge to take measurements of the force on the sphere when it was suspended and stationary in the liquid.
When the sphere was stationary, the reading on the force gauge was 0.20 N.
The student then moved the force gauge upwards so that the sphere moved at a constant speed. They determined this value of speed by taking the following measurements
- distance moved between the rubber bands = 25.0 cm
- time taken to move between the rubber bands = 0.78 s
When the sphere was moving at constant speed, the reading on the force gauge was 0.29 N.
3 marksDiscuss which measurement contributes the largest source of uncertainty in the determination of viscosity.
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