First, the hour hand

There are two kinds of needle-like parts on the surface of the timer, such as hands indicating hours and clocks. Short hands indicate hours and are called "hour hands".

Clockwise means turning in the same direction as the clock. The reason why the hour hand rotates clockwise stems from its predecessor, the sundial. The hour hand first appeared in the northern hemisphere, and its function is similar to the "shadow pointer" projected by the sundial on the ground.

The sun rises in the east and sets in the west, and its shadow on the sundial runs in the opposite direction, from west to east, so the numbers representing time on the sundial are arranged in this way, and the numbers on the surface of modern clocks follow this arrangement.

Counter-clockwise is the antonym of clockwise, representing counter-clockwise rotation. Whether the object rotates clockwise or counterclockwise is related to the observation angle. For example, when viewed from directly above the North Pole, the rotation of the earth is counterclockwise, and when viewed from directly above the South Pole, the rotation of the earth is clockwise.

Second, the minute hand

The minute hand refers to the hand that moves in minutes on the clock. When the minute hand moves on the clock, it needs 1 minute, and the rotation angle is six degrees. When a number moves, it takes five minutes and the rotation angle is 30 degrees.

Mathematical application of hour hand and minute hand

I. Time calculation

By observing the position of the hour hand and the minute hand, the elapsed time can be calculated. If the hour hand points to 12 and the minute hand points to 3, it means that 15 minutes have passed.

Second, the proportion and proportion:

The hour hand and the minute hand can be used to solve the problem of proportion and ratio. If the hour hand walks 30 degrees per hour and the minute hand walks 360 degrees per hour, the speed ratio between the hour hand and the minute hand is 1: 12.

Third, the angle measurement

The position of the hour hand and the minute hand can be used to measure the angle. At that time, when the pointer and minute hand both point to 12, the angle between them is 0 degrees; At that time, when the pointer pointed to 12 and the minute hand pointed to 6, the included angle between them was 180 degrees.

Fourth, the relationship between quality and speed.

If the hour hand and minute hand of a clock are regarded as a system, the relationship between their mass and speed can be applied to mechanical problems.