What is a stopwatch? What is the least count of a mechanical stopwatches you have used in the laboratories? 

Difficulty: Easy


A stopwatch is used to measure the time interval of an event.


Mechanical stopwatch:

A mechanical stopwatch can measure a time interval up to a minimum of 0.1 seconds.

The least count of the mechanical stopwatch is 0.1 seconds.


Digital stopwatch:

Digital stopwatches commonly used in laboratories can measure a time interval as small as 1/100 second or 0.01 second.

The least count of the digital stopwatch is 0.01 seconds.


How to use a Stopwatch:

Use of a mechanical stopwatch:

A mechanical stopwatch has a knob that is used to wind the spring that powers the watch. It can also be used as a start-stop and reset button. The watch starts when the knob is pressed once. When pressed the second time, it stops the watch while the third press brings the needle back to zero position.                                                                                       


Use of a digital stopwatch:

          The digital stopwatch starts to indicate the time lapsed as the start/stop button is pressed. As soon as the start/stop button is pressed again. It stops and indicates the time interval recorded by it between the start and stop of an event. A reset button restores its initial zero settings.



A school laboratory must-have safety equipment such as:

  • Waste-disposal basket
  • Fire extinguisher. S
  • Fire alarm.
  • First Aid Box.
  • Sand and water buckets.
  • Fire blanket to put off the fire.
  • Substances and equipment that need extra care must bear proper warning signs such as given below:

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