All formulas and analysis of physics in grade three of junior high school

In the mechanical part, 1. Velocity: v = s / T2, gravity: g = mg3, density: ρ = m / V4, pressure: P = f / S5, liquid pressure: P = ρ gh6, buoyancy: F floating = f '- f (pressure difference) f floating = G-F (apparent gravity) f floating = g (floating, suspension) 7. Archimedes principle: F floating = g row = ρ

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1. Physics calculation from grade one to grade three When shooting, the distance between the target and the shooter is 300 meters. After shooting for 1.4 seconds, the shooter hears the sound of hitting the target, and the sound speed is 300 meters per second. Calculate the average flight speed of the bullet
2. A thin-walled cylindrical container with a mass of 2kg and a bottom area of 400cm2 is placed on a horizontal table. A certain liquid with a depth of 25cm is injected into the container. At this time, the pressure of the liquid on the bottom of the container is 1960 PA? The above process and formula are needed, and G is 9.8 n,
3. A 40kW car runs at a speed of 0.5m/s on a straight road The resistance to the car 2. Work done by the car after 1.5h
4. Physical density of grade three 1. There is water in a cylindrical container. The distance between the water surface and the upper edge of the container is 7cm. When the water forms ice, the upper edge of the container is 5cm. The depth between the water surface and the bottom of the container is calculated
5. In the experiment of measuring the liquid density, a student lost the step of measuring the mass of the cup in advance, but it measured the volume of the liquid twice and the total mass of the liquid and the measuring cup Liquid and measuring cup mass g liquid volume cm square The first time 21.4 16.5 The second time 39.9 35.0
6. Is the ratio of mass to volume the same for the same substance reasonable or wrong? How to correct it?
7. Xiaodong wants to estimate the density of some kind of oil, ρ oil. The measuring tool he has is only a scale. Xiaodong uses the equipment around him to design an experimental scheme. First, find a straight hard rod, hang it at o point with a thin line, and the hard rod is balanced in the horizontal position. Then hang the metal block B with known density of ρ at C on the left end of the hard rod, and find a weight a at the right end of the hard rod, and adjust the weight a At this time, the position of the weight hanging on the hard rod is e, as shown in the figure. The following is part of the experimental steps for Xiaodong to measure ρ oil. Please complete the experimental steps according to Xiaodong's experimental ideas (1) Measure the length l0 of OE with a scale; (2) immerse the metal block B in the oil to be measured, and move the weight a from e to D, and the hard rod will be balanced in the horizontal position again; (3)___ (4) the formula for calculating ρ oil by using the physical quantity measured above and the known quantity in the question is as follows:___ ．
8. Are Archimedes law and Archimedes principle the same concepts? If they are different, please tell us the difference,
9. How to convert mole per liter into milligram per liter
10. Conversion of molmin / L and molsec / L
11. A piece of wood has a volume of 100 cubic centimeters and a density of 600 kg / m3. What is the buoyancy of the wood at rest
12. A block of wood has a volume of 100 cubic centimeters and a density of 600 kg / m3. When you press it all into the water by hand, how much buoyancy does the block bear?
13. The volume of the wood block is 100 cubic centimeter, and the density is 0.6 * 10 cubic meter. Q (1) when you press it into the water, what is the buoyancy of the wood block (2) How much pressure does the hand put on the block at this time?
14. The volume of a piece of wood is 200cm3, and its density is 0.8 times 10 cubic kilogram per cubic meter. If you immerse it in the water and let it go, why can't the piece of wood be suspended in the water? When the piece of wood finally floats on the water, how large is the volume immersed in the water when it is still?
15. A piece of wood has a volume of 200 cubic centimeters and a density of 0.8 * 10 cubic kilograms per cubic meter. Immerse it in water and let it go. Why can't a piece of wood be suspended The volume of a wood block is 200cm ^ 3, and the density is 0.8 times 10 ^ 3kg / m ^ 3. Let it go after immersing it in the water. Why can't the wood block be suspended in the water? When the wood block finally floats on the water, how large is the volume immersed in the water when it is still?
16. A piece of wood has a volume of 200 cubic centimeters and a density of 0.8 * 10 cubic kilograms per cubic meter. Immerse it in water and let it go. Why can't a piece of wood be suspended
17. What's the difference between Luhua 5S pressed first-class peanut oil and pressed first-class peanut oil? Which one has better effect?
18. Is it good for your health to eat the first grade peanut oil squeezed by Luhua 5S? Do you have any side effects?
19. What is the density of peanut oil?
20. How many kilos is five liters of Luhua peanut oil equal to As above