You may have noticed that a few sharp jerks are given to clinical thermometer before using it. Why is it done so ?

Explanation

### Step-by-Step Solution:

1. **Understanding the Clinical Thermometer**: A clinical thermometer is used to measure body temperature. It contains mercury in a glass tube.

2. **Initial Position of Mercury**: Before using the thermometer, the mercury level is usually above the normal temperature range. This happens because the thermometer may have been used previously or has been exposed to higher temperatures.

3. **Purpose of the Jerks**: Giving a few sharp jerks to the thermometer helps to reset the mercury level. The jerks create a force that allows the mercury to move down the tube.

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