A small experiment in physics

Observe the diffusion phenomenon

Prepare a cup of cold water and a cup of hot water, put two small potassium permanganate into two cups of water respectively, and try to observe and compare the diffusion of potassium permanganate in two cups of water. If you observe the difference in potassium permanganate diffusion between two glasses of water, think about what this means.

Experiment 2

Feel atmospheric pressure

Take an empty aluminum can and a basin of cold water, wrap the iron wire around the mouth of the can and fix it, and twist the iron wire into a handle (with a certain length and strength). Add a small amount of water to the pot, put it on an alcohol lamp and heat it until it boils, and continue heating for dozens of seconds. Quickly (holding the wire handle) pour the cans into cold water and observe the phenomenon. Note: At this time, the cans are squashed under the action of air pressure, making a loud noise. The experimenter should be psychologically prepared to avoid being burned or even causing a fire when encountering other experimental instruments in a panic. This experiment is dangerous to some extent, so it is suggested to be carried out under the guidance of the teacher.

Experiment 3

Amplitude exchange

Prepare two pendulums with the same pendulum length (the pendulums are heavier) and a thin nylon rope, fix both ends of the nylon rope at high places respectively, and tie the upper ends of the two pendulums in the middle of the nylon rope, and the distance between the suspension points shall not exceed 10 cm (check whether the pendulums are the same when fixing). Put one pendulum in a vertical position, pull the other pendulum to a certain position in the direction perpendicular to the nylon rope (there is no need to have a five-degree angle limit), let it vibrate in the direction perpendicular to the nylon rope, and observe the amplitude changes of the two pendulums (it may take a long time to see, and the required time depends on the device). It can be seen that the amplitudes of the two pendulums will be constantly exchanged.

Experiment 4

Try the taste of electrostatic shock.

Wash, rinse and dry the plastic frisbee with washing powder; Prepare a circular iron sheet, slightly smaller than a frisbee, make a small hole in it, tie it with a 20 cm long silk thread through the hole, rub the inside of the disc with a piece of dry fur, and then take it away quickly. Then put the iron sheet into the disc, with one end of the silk thread in your hand (to prevent your hand from touching the iron sheet), so that the charge on the disc will accumulate on the iron sheet, which will be slightly when you approach the iron sheet with your finger. At the same time, you can also see the electric spark and hear the sound of discharge (this is because the voltage is high, but the current duration is short, because the power is small. Although there is slight numbness, it does not endanger people's life and health). Note that the effect of this experiment is greatly influenced by the environment. Generally speaking, it is easier to succeed in dry weather than in humid air, and it is easier to succeed in sunny days indoors than in crowded rooms. It is easier to succeed outdoors than indoors.

Experiment 5

Will electrostatic induction occur when water is liquid?

Turn the household tap water switch to trickle, and put the plastic rod (or plastic comb or pen container) brushed with fur near this trickle, and you will clearly see that the water is bending in the direction of the plastic rod.

Experiment 6 Why is the bulb resistance measured by ohmmeter less than the calculated value?

For a light bulb "220V25W", the filament resistance can be calculated as1936Ohm according to the electric power formula. Use an ohmmeter to measure whether the measured resistance is large or small, and why?

Experiment 7

Which bottle rolls fast?

Two identical glass bottles, one filled with sand and the other filled with water, slide down the same slope. Which bottle rolls faster? Try it, think about it, why?

Experiment 8

Can the wooden ruler keep level?

There is a wooden ruler with a length of 1 m. Support both ends of the wooden ruler horizontally with the left and right index fingers respectively. At this time, the left and right fingers are close to each other. Can the wooden ruler remain horizontal? What should I do if my left and right fingers are close at the same time? (Hint, related to the knowledge of friction and torque)

Experiment 9

Why doesn't the water overflow?

Pour half a glass of water into the cup and cover it with paper. Press the paper with your palm and turn the cup over. Be careful not to spill the water in the cup. Let go, neither the water nor the paper in the cup will fall. It doesn't matter even if you put some small things like wooden screws in the water. Why is this?

Experiment 10

How to make a simple pendulum swing

Make a simple pendulum with a nylon thread about one meter long and a padlock. You need to blow air to swing it. The swing solution is required to reach about 30 degrees. In this process, the distance between the mouth and the balance position of the simple pendulum should be kept above 0.5 meters, and the body or any other object should not touch any part and suspension point of the simple pendulum. Try to achieve your goal and think about why.

Copy it down and organize it yourself.