Do interesting physics experiments with "empty milk cartons and straws"

First, prove the existence of atmospheric pressure.

1. As shown in Figure 1, block the upper end of the straw with your fingers and move the water from Cup A to Cup B. In the process of moving the straw, the water in the tube will not fall due to the atmospheric pressure, indicating the existence of atmospheric pressure;

2. Take an empty milk box, blow enough air into it through the straw to make it expand, and then slowly suck out the gas through the straw. You will find that the box is deflated, indicating the existence of atmospheric pressure.

Second, demonstrate the relationship between fluid pressure and flow.

As shown in Figure 2, the cups of two paper cups ("green arrow" paper cups) are nested upward, and the outer paper label is held by hand, and air is forcibly blown above the cups, which is parallel to the cups. The paper cup inside will jump up, because the gas above is fast and the pressure is low, while the gas below is slow and strong, resulting in an upward pressure difference, so it will jump up, indicating that "the higher the speed, the lower the pressure."

Third, demonstrate the relationship between internal pressure and liquid depth.

Punch three holes of the same size on the side of the empty paper box. After the paper box is filled with water, the water is ejected from the small hole, as shown in Figure 3, which shows that "the pressure inside the liquid is related to the depth of the liquid, and the deeper the depth, the greater the pressure".

Fourthly, make a densitometer.

Take a straw, fill it with a proper amount of colored plasticine, and then put it in water to make it float, thus making a simple densimeter (as shown in Figure 4).

Five, the production of "earth phone"

As shown in Figure 5, the "Earth Phone" is made of two empty paper cups and a cotton thread, as shown in Figure 3. If the line is not straightened and is in a relaxed state when using the "earth phone", then the listening party cannot hear the other party's voice through the cotton thread; If another student holds a part of the thread by hand when using the "earth phone", the listener will not hear the sound, because "when holding the thread by hand, it hinders the transmission of vibration on the cotton thread"; The communication between 65438 and 200m can be realized by using "earth phone", which shows that "cotton thread (solid) can transmit sound"; At the same distance, the speaker speaks at the same volume. If you connect the "earth phone" with a thin metal wire, you will hear louder sound, which means that "thin metal wire is easier to transmit sound than cotton wire".

Six, pinhole imaging production and demonstration

Using empty paper cups and translucent film as shown in Figure 3 to make pinhole imager (the opening end is covered with translucent film and the bottom is punched with a pinhole) is easier to make than using cans, and the operation is more labor-saving, convenient and effective.