Turn the button and wind it up. This is the power of stopwatch movement. Press the button with your thumb and the stopwatch will start timing; Press the button again, the stopwatch stops moving and starts reading; Press it again, and the stopwatch will return to zero, ready for the next time.

Introduction to physics:

Physics is a subject that studies the most common laws of motion and the basic structure of matter. Physics, as the leading discipline of natural science, studies the most basic motion forms and laws of all substances from the universe to elementary particles, so it has become the research basis of other natural science disciplines.

Physics began in the era of Galileo and Newton, and now it has become a basic science with many branches. Physics is an experimental science, and it is also a science that advocates rationality and attaches importance to logical reasoning. Physics, which makes full use of mathematics as its working language, is the most accurate natural science subject today.

Physics is a regular summary of people's understanding of the movement and transformation of substances in nature, which should be two kinds. One is the extension of early people through sensory vision; Second, since modern times, people have indirectly understood the internal composition of matter by inventing scientific instruments and experimental results for observation and measurement.

Physics can be roughly divided into two parts from different research angles and viewpoints: macro physics does not analyze the individual effect of particle swarm, but directly considers the overall effect, which has appeared at the earliest;

The birth of microphysics stems from new experimental phenomena such as blackbody radiation, photoelectric effect and atomic spectrum. This is something that macro physics can't explain well. It is a revision of macroscopic physics and is gradually improved with the development of experimental technology and theoretical physics.

Physics is a natural science, which mainly studies matter, energy, space and time, especially their respective properties and their relationships. Physics is knowledge about the laws of nature; More broadly, physics explores and analyzes what happens in nature to understand its laws.