The instrument for measuring time is a clock, which often stops to measure time in sports fields and laboratories.
Generally speaking, time measurement includes: time interval measurement and time measurement.
Timing tools mainly include stopwatches, watches, clocks, sundials and hourglasses used in ancient times.
Use and reading of mechanical stopwatch;
1. How to use the mechanical stopwatch? Wind it up before use. When measuring, hold the stopwatch with your hand and press the "Start/Stop" button with your thumb, and the stopwatch pointer will immediately move to start timing. Press the "Start/Stop" button again, the stopwatch hands stop walking, and the hands indicate the elapsed time when the music is pressed twice; After the measurement is completed, press the "Reset" button, and the second hand and minute hand will bounce back to the origin (zero scale).
2. Use a mechanical stopwatch to read and record data.
(1) When the measured time exceeds 0.5 min, the integer multiple of 0.5 min is read by the scale indicated by the minute hand in the small round dial, and the part less than 0.5 min is read by the scale indicated by the second hand in the large round dial. The measured total time is the sum of the readings of two hands (minute hand and second hand), that is, t = minute hand indicator (t 1)+ second hand.
(2) Generally, you can't estimate it when you look at the stopwatch. This is because the stopwatch is a mechanical watch, and its hands turn by gears. The pointer can't stop between two squares, but it must stop on the scale line.
3. Matters needing attention when using stopwatch
(1) Before using the stopwatch, check whether the stopwatch hands are aligned with the zero point. If it can't be centered, write down the value indicated by the second hand at this time and correct the reading;
(2) Different stopwatches have different minutes. Please observe carefully before measuring:
(3) Don't knock the stopwatch in the experiment to avoid damage;
(4) After the measurement is completed, the stopwatch should continue to move, so that the clockwork can be completely relaxed and return to a relaxed state.