What is the shortest distance in physics? down to centimeters

In fact, theoretically there is no shortest distance, can you name what it is to separate centimeters n times?

The speed of sound propagation in the air with a moderate temperature of 15 degrees Celsius is 340 s, first of all, 1000km is converted into 1000000m, 1000000 340 is about equal to 2941, and then 2941s is converted into hours, and the final result is about hours, and it takes about hours to travel from Beijing to Shanghai (2) The speed of the train is 100km s, the distance is 1000km, and 1000 100=10, so it takes 10 hours for the train to travel from Beijing to Shanghai (3) The speed of a jumbo jet is 600 km, the distance is 1000 km, and 1000 600 is about equal to an hour, so it takes about an hour for a jumbo jet to travel from Beijing to Shanghai.

Based on the average speed of a train of 100 km/h, it takes 1000 km (100 kmh) = 10 hours, which is about 10 hours.

Take D29 as an example, the train departs at 7:47 a.m. and arrives at 18:52 p.m., taking 11 hours and 5 minutes.

Based on the estimation of the speed of an airplane at 500 km per hour, 1000 km takes 1000 km (500 km h) = 2 hours, that is, about 2 hours.

Take China Eastern Airlines MU5198 as an example, it departs at 22:50 in the evening and arrives at 00:55 in the morning, which takes 2 hours and 5 minutes.

The current domestic train speed is 160 km/h, so it takes time 1000 160 = hours, and the speed of a jumbo jet is 940 km/h, so it takes time 1000 940=h.

First convert 1000km to 1000000m, and then divide 1000000m by the speed of sound propagation in the air at room temperature, which is 340m s is about 2941s

This kind of problem is easy to solve.

Question 1. See**.

The speed of the divinely propagating sound in the railroad tracks in the second question is unknown, and the question should be suspected, but the loss of the Siliang is about the same as the first body.

What's the problem??

I didn't understand.

The eye muscles do not need to be tense and are in a relaxed state, so they are not prone to myopia.

The mirror has only one side of the mirror. On the other side is paint. Block light.

There are two images of glass. The distance between the two images is equal to the thickness of the glass.

He said the tip of the pen to his own likeness. You have two imaging faces.

The distance from one of the images to the nib of the pen is 0It is the image of the face of the city that the tip of the pen touches. Because the distance is one.

So consider another scenario. That is, the back of the pen where the tip of your pen touches.

The distance from that side of the image is equal to the distance from the tip of the pen to that side.

The sum is equal to 1 cm

So the glass thickness is.

I'm tired of typing.

Give it points. Thank you.

The back side is used to block light, just like the reflection in the water is imaged on the surface of the water, and if the back is transparent, the light can continue to penetrate.

x,l,s。In our Harbin high school textbook, it is x, and the junior high school textbook is s.

The lowercase letter s indicates; Uppercase s indicate area.

l or the uppercase of both endpoint letters, such as ab

Choose A, because the object is 2cm high, and the image height is 4cm, it means that it is a magnified real image, to become a magnified real image, the object must be between 1x the focal length and 2x the focal length, knowing that the focal length of the convex lens is 5cm, then the object should be between 5cm and 10cm, so you can only choose A

The answer to b is greater than 2 times the focal length of Zheng Qin's noise, which is a real image of shrinking.

The answer is less than 1x the focal length, which is a magnified virtual image, and it is impossible to image on the light screen.

D answer 10cm is equal to 2 times the focal length, and the first thought is the same large real image.

A because the object is 2 cm, like 4 cm of the Ant Wang imitation, is magnified, and can be imaged on the light screen, indicating that it is a real image, and the object distance is between the 1 times the focal length of the stuffy fiber and the 2 times the focal length, so choose A

It takes a while for a car driver to operate the brakes through muscle movements from the time they notice the situation, and this time is called reaction time. During this time, the distance the car travels is called the reaction distance. [Reaction distance = vehicle speed reaction time.] 】

From the time the brake is operated to the time the car stops, the car has to move forward for a certain distance due to inertia, which is called the braking distance. The braking distance of the car can reflect the quality of the car's braking performance.

The sum of the reaction distance and the braking distance is the parking distance of the car. The stopping distance of the car is related to the speed of the vehicle, the reaction time of the driver, the road conditions, the braking performance of the car and other factors.

If the car is driving at a speed of 90km h on asphalt or concrete pavement, if the driver's reaction time is based on the speed formula, the reaction distance can be calculated according to the speed formula, and the braking distance is about 45m after testing.

Article 36 of the "Road Traffic Management Regulations" promulgated by the Ministry of Communications limits the maximum speed of motor vehicles when they encounter different situations in driving, such as when motor vehicles are driving on ice, snow and muddy roads, the maximum speed is not allowed to exceed 20km h, and tractors are not allowed to exceed 15km h. Article 37 stipulates that for motor vehicles driving in the same lane, the vehicle behind must keep the necessary safety distance from the vehicle in front according to the driving speed, weather and road conditions. For example, when the speed is 100 km/h, keep a distance of 100 m.

By following these regulations, drivers can effectively prevent rear-end collisions in motor vehicles.

People have a certain reaction time, so the proposed model is: the car first moves at a constant speed, then decelerates evenly, and finally stops.

Let's consider the acceleration of the car's brakes and the speed of the person's reaction. Oh, the specific formula is unknown, take a look at the following**.