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On the physics of density, 1. If the mass ratio of a and B is 1:4, the volume ratio of a and B is 1:4_____ And the density ratio is_____ . 2. A city has decided to use a special alloy material to cast a statue of a hero who has done a good deed. The height of the statue is 1.75m. In the design, the same metal material is used to cast a scaled down sample. The height of the sample is 17.5cm and the mass is 700g. Then, what is the mass of the finished product of the hero statue? 3. There is a shot with a volume of 2.5 square decimeters and a mass of 22.6kg. Is the shot solid or hollow? If it is hollow, what is the volume of the hollow part?
1. 1:4 1:1 is obtained from the density formula
2. 700×1000=700kg
3. Density: 9.04 g / cm3
There is a glass bottle with a mass of 0.1kg. When the bottle is filled with water, the total mass of the bottle and water is 0.4KG. When the bottle is filled with metal particles, the total mass of the bottle and metal particles is 0.8kg. If the bottle is filled with water again, the total mass of the bottle, metal particles and water is 0.9kg
If you hear the echo after clapping for 2 seconds, ask for the distance between the person and the obstacle
2X340/2=340M
The propagation speed of sound in the air is 340m / s. if the distance between a person and a mountain is 510m, the person shouts to the mountain and passes______ The echo can be heard in seconds
According to the definition of echo, let time be t, t = s / v = 510m × 2 △ 340m / S = 3S
Xiaoyu's car is driving towards a high mountain cliff at the speed of 15km / h per hour. The driver hears the echo after 5 minutes of honking his horn. How far is the distance between the car and the cliff? (the speed of sound propagation in the air is 340m / s)
(5/18*15+340)*5*60/2=51.625km
Someone shot somewhere in the 1200 meter wide Grand Canyon. After the shooting, he heard two echoes. They were reflected from the cliffs on both sides. The interval between the two times was 5S. How many meters was the shooting position from the nearer cliff?
If you want to finish before 9 o'clock, you can continue to add scores
Set the shortest distance s
The first echo time T1 = 2S / 340m / S
The second echo time T2 = 2 (1200m-s) / 340m / S
The interval time between two times is 5S = t2-t1 = 2 (1200m-s) / 340m / s-2s / 340m / s
S = 175m
There is a high mountain in front of the car. The car runs at a constant speed of 12 m / S & nbsp;. Two seconds after the car whistle, the driver hears the echo. How far is the car from the high mountain at this time? (set the sound propagation speed in the air as 340m / s)
If the distance between the car and the mountain is s ″ = 12 (s + s ′) = 12 × 704M = 352m, and the distance between the car and the mountain in front is S1 = s ″ - S = 352m-24m = 328m when the echo is heard, the distance between the car and the mountain in front is 328m
Simple calculation of echo
The distance between two buildings is 170 meters
Liming and Zhanbin are standing on the corridor of the two buildings. Liming shouts Zhanbin that the air temperature at that time is 15 ℃
1: How many seconds does it take for the sound to spread from Liming to Zhanbin?
2: How long after dawn do you hear your own echo?
3: Why does dawn put his hand on his mouth to make a trumpet when he shouts Zhan bin?
1:170m/340m/s=0.5s
2:170m*2=340m
340m/340m/s=1s
3: Gather sounds together to make them easier for another person to hear
1. Knock on one end of a long hollow steel pipe, and the sound can be heard twice at the other end of the steel pipe, with an interval of 0.2S. What is the length of the steel pipe? (the speed of sound in the steel pipe is known to be 5200m / s)
2. A team of 12 meters long marched at the speed of 1.4 m / s. at the end, a correspondent wanted to inform the platoon leader because of something. He felt the platoon leader from the end at the speed of 2.6 m / s. how long would it take?
3. When a ship sails between two docks, it takes 3.5 hours to go downstream and 5 hours to go upstream. The current speed is 2 kilometers per hour. Find out the speed of the ship sailing in still water
PS: if you can, there must be a reason,
1. Suppose that the time of sound propagation in the air is t: 340t = 5200 (t-0.2)
t=0.214s
So the length of steel pipe: S = 5200m / S (0.214s-0.2s) = 72.8m
2. The speed of correspondent relative to march is: v = 2.6-1.4 = 1.2m/s
So t = s / v = 12 / 1.2 = 10s
3. Because V forward = V static + flow velocity. V reverse = V static - flow velocity
S = V CIS * t CIS = V inverse t inverse
So: (V Jing + 2) * 3.5 = (V Jing - 2) * 5
From this we can calculate vstatic = 11.3m/s
The monument in the alley of Huanghua road "tears of blood sprinkle on Huanghua", bearing in mind a period of history of Japanese invasion of China and a share of blood debt owed by Japan to the Chinese people. The height of the monument is about 1.5m, the width is about 0.6m and the thickness is about 0.1M. The known density of the monument is 2.6 * 10 & sup3; kg / M & sup3; (g = 10N / kg)
① The weight of the monument;
② Its pressure on the ground
1. Volume: 1.5 * 0.6 * 0.1 = 0.09m ^ 3
So in the cup: 0.09 * 2.6 * 10 ^ 3 = 234kg
2. Pressure is gravity: 234 * 10 = 2340n
Pressure: 2340 / 0.6 / 0.1 = 39000pa
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