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The meaning and calculation formula of 1 ＼ G 2. On buoyancy formula
1. 2. Archimedes principle: F floating = g row = PGV. The buoyancy of the liquid is the gravity of the liquid. 3. State method: F floating = g when the object is in suspension or floating
Using the pulley block as shown in the figure to lift the goods, it is known that the weight of the moving pulley is 30n, the weight of the goods is 360n, the rising speed is 0.3m/s, and the power of the pulling force F is 180W (excluding the weight of the rope)
It is known that: g = 360n & nbsp; g = 30n & nbsp; V1 = 0.3m/s & nbsp; P = 180W & nbsp; n = 3 & nbsp; H = 3M, find: (1) η =? （2）Wf=？ (1) The speed of hand pulling rope is V2 = 3v1 = 3 × 0.3m/s = 0.9m/s, ∵ P = WT, ∵ the tension acting on the free end of rope is f = PV = 180w0.9m/s = 200N
The formula w / wtotal = f pull H / Fs, which takes into account the dead weight of moving pulley, friction resistance, rope weight and other additional work when pulling objects in vertical direction
W useful / W total = GH / Fs s = NH
The formula of substituting f = (g matter + G motion) / n into the above formula is as follows:
W useful / W total = g matter / (g matter + G movement)
That is to say, when the pulley block with movable pulley does work, the extra work is the work done by the pulling force on the movable pulley. The heavier the movable pulley is, the lower the mechanical efficiency is
As shown in the figure, the weight of object a is 240n, the weight of movable pulley is 60N, and the force F will lift the object vertically at a speed of 1mgs. If the weight and friction of the rope are not taken into account, what is the size of the pull f______ &After 1 s, the work of pulling force F is______ &J, power is______ &What is the mechanical efficiency of the device______ ．
According to the figure, n = 2, (1) regardless of rope weight and friction, f = g object + G motion, 2 = 240n + 60n2 = 150n; (2) height of object rising: H = 1m / s × 1s = 1m, distance of pulling force moving: S = 2H = 2m, pulling force work: wtotal = FS = 150n × 2m = 300j, pulling force work power: P = wtotal t = 300j, s = 300W; (3) wyou = GH = 240n × 1m = 240j, mechanical efficiency of this device: η = wyou, wtotal = 240j300j = 80% 50；300；300；80%．
A moving pulley is used to raise the weight of 500N by 0.5m at a uniform speed, and the tension applied at the free end of the rope is 300N, then the total W is 0.5m=______ J. W is useful=______ J. Mechanical efficiency η=______ ．
∵ the goods and moving pulley are borne by two sections of rope, ∵ s = 2H = 2 × 0.5m = 1m, ∵ f = 300N, ∵ wtotal = FS = 300N × 1m = 300j, ∵ objects weighing 500N rise by 0.5m, ∵ the effective work of the machine is w = GH = 500N × 0.5m = 250j, so the efficiency of the machine is η = w, and wtotal = 250j300j ≈ 83.3%. So the answer is: 300250, 83.3%
G wheel = w / NH (where n is the number of ropes on the moving pulley and H is the rising height of the moving pulley)
It's wrong
I don't want it
This is only considering the gravity of the moving pulley, not considering the friction
In the formula P = w / T, does w refer to the active work or the total work
W refers to the active work or the total work? It can be the work done by an object or the total work. In the same formula, W and P only need to correspond. That is to say, W is the total work, and the resulting P is the total power. W represents the work done by a force, and P is the power of a force
Give you work, pull force F, mechanical efficiency. How do you find the distance s of the free end of the rope
According to η = wyou / wtotal, the total work wtotal can be obtained
According to wtotal = FS, the distance s of the free end of the rope can be obtained
Is the formula of S = ns and V = Nv of moving pulley also applicable to the calculation of fixed pulley?
Of course, s rope = NH material, V rope = NV material
Calculation formula of physical mechanical energy and work, calculation of useful work, etc
RELATED INFORMATIONS
- 1. The formula of buoyancy
- 2. Xiaohua did the experiment of "estimating the value of atmospheric pressure." (1) please complete the following experimental steps. A. push the piston of the syringe to the top of the syringe barrel______ Then seal the small hole of the syringe with a rubber cap. B. fasten the neck of the piston of the syringe with a fine nylon rope so that one end of the rope is connected with the hook of the spring dynamometer, and then pull the syringe barrel horizontally and slowly to the right______ Write it down______ It is equal to the pressure of the atmosphere on the piston, F.C______ , denoted as l, read out the volume V of the syringe, then the area s of the piston=______ Finally, the value p of atmospheric pressure at this time is calculated=______ (write the expression with the measured quantity). (2) in the experiment, Xiaohua used the measuring instrument correctly, and the reading was correct, but she found that there was always deviation in the measurement results, which may be caused by (write two points)______ ．
- 3. Typical problems in junior high school physics
- 4. As shown in the figure, a piece of lead is hung under an inflated balloon with a thin thread, put it into the water, and it is just in a static state somewhere. If some water is slowly released from the bottom, the lead and the balloon () A. Still able to stand still B. move down C. move up D. stand still. It's possible to move up or down
- 5. 1. The buoyancy of a small ball with a volume of 2x10 cubic meters and a volume of negative cubic meters is - Niu if it is completely immersed in water. If half of its volume is immersed in water, the buoyancy is - Niu 2. When the gravity of the metal block is 26.5n and the metal block is suspended by a spring scale and immersed in water, the indication of the spring scale is 16.7n. The buoyancy of the metal block under water is - n 3. An object weighing 4 N, with a volume of 0.5 cubic decimeter, will be completely immersed in water, and the buoyancy it receives is - cow, it will lose weight in water—— 4. If a piece of wood weighs 20n and floats on the surface of the water and is still, the buoyancy of the piece of wood to the water is - Niu 5. An ocean going ship sailed into the Huangpu River from the East China Sea. The ship realized the buoyancy it received
- 6. How is the buoyancy formula derived?
- 7. How to deduce the formula of buoyancy?
- 8. Calculation formula of water buoyancy V row It is the calculation formula of V row, f floating = P liquid GV row
- 9. Buoyancy formula of water Who knows
- 10. What is the formula of buoyancy
- 11. All formulas of buoyancy Buoyancy knowledge explains all the variant formulas of buoyancy
- 12. buoyancy A and B are liquid and solid respectively. The density of liquid a is 1g / cm3, and that of solid B is 0.5g/cm3. When a solid solid (composed of substance B) with a volume of 10-3m3 is put into a container containing enough liquid of substance A, how much buoyancy does the solid solid receive when it is still? How much volume does the liquid displace?
- 13. In a bathing beach, the bottom of the water is full of stones. In the process of swimming from deep water to shallow water, the following experience and analysis are reasonable () A. Feet are getting more and more painful because water has less and less support for people. B. feet are getting more and more painful because people are receiving more and more gravity. C. feet don't hurt because people are getting lighter and lighter. D. feet don't hurt because water has more and more support for people
- 14. Who listed the related formulas of physical pressure and buoyancy one by one, including Rou = m / V, which is not published in textbooks? Don't take too many words to explain in front of me. Just tell me what the physical quantity is. I want to copy and paste it
- 15. A course of junior high school physics [pressure and buoyancy], This is the physical simulation of Haidian District in Beijing in 2009 As shown in the figure (a cylindrical container contains a plastic box, in which an iron block floats on the water surface), the cylindrical container with bottom area S1 contains liquid with unknown density. Put a cube metal block with density ρ into the rectangular plastic box with bottom area S2 (the thickness of the plastic box can be ignored), The plastic box floats on the liquid surface (the liquid will not overflow the container), and its immersion depth is H1. If the metal block is taken out of the plastic box, it is tied under the plastic box with thin wire, and put into the liquid, the metal block does not contact the container, and the immersion depth of the plastic box is H2. Cut the thin wire, the metal block will sink to the bottom of the container, and the plastic box floats on the liquid surface, The depth of immersion is H3. If the plastic box is always upright without inclination, the pressure of the liquid on the bottom of the cylindrical container is reduced before and after the thin line is cut? Two supplementary points: 1. The density of the liquid in the container is unknown, and the expression should not contain ρ liquid. 2. The question is how much pressure has been reduced. Not why.
- 16. All the formulas for buoyancy and pressure
- 17. When measuring the density of a small solid object, a physics interest group adopted the following experimental operations: first, the mass mo of the object was measured with a balance; then, a certain amount of water was put into a small beaker, and the total mass M1 of the beaker and water was measured with a balance; then, after the object was tied up with a thin line, the mass M1 of the beaker and water was measured, The object is immersed in the water of the beaker (the water does not overflow and the object does not touch the beaker) by holding a thin line in hand. At this time, the measured value of the balance is m2, as shown in Figure 6 A. The buoyancy of an object in water is MOG B. The buoyancy of an object in water is (m2-ml) g C. The density of the object is Mo / m2-m1 * P water D. The density of the object is Mo / m2-m0 * P water 、 I don't understand at all. I'm going to take the senior high school entrance examination right away. It's really disturbing that I don't understand
- 18. Some questions about buoyancy in junior high school physics 1. A 100 cubic centimeter object is hung under the spring dynamometer. When the object is immersed in water, the indication of the spring dynamometer is 1.7n__ N 2. Put a solid aluminum block with a mass of 27g into a beaker filled with water. When the aluminum block is still in water, the mass of water discharged from the beaker is__ g. Put the aluminum block into a beaker filled with alcohol, and the mass of the discharged alcohol is__ g
- 19. Under what conditions is f floating = ρ liquid GV discharged, under what conditions is f floating = g discharged, f floating = m discharged, G discharged
- 20. The physical meaning of G = 9.8n/kg is______ ．