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Using the lever theorem, Give you a pen, a meter ruler, and some 50g weights to calculate the mass of the ruler
It's very simple. Place the pen as a fulcrum at 20cm of the ruler. Then put weights on the short part of the ruler until the long part of the ruler just gets up. Let's see how many weights are 50 grams (set as x)
The mass of the ruler is m G
50X×20＝(4/5)M*40
M=(25/8)X
Application of lever principle in life (ten cases)
Spanners, doors, toilets, scales, scales, bicycle pedals, scissors, can openers, pliers, nail clippers, automatic locks, light switches, screwdrivers, train rail exchange control rods, etc
Lever principle in life
Labor saving lever:
Claw hammer, bottle cap lifting, spike prying, vice, driver, trolley, iron sheet cutting and pruning scissors
Leverage:
Chopsticks, tweezers, fishing rod, pedal, broom, paddle, tailoring scissors, hairdressing scissors, human arm
Equal arm lever:
Balance, fixed pulley
example:
1. Take bicycle as an example
Bicycle is a commonly used means of transportation. From the perspective of its structure and use, it requires a lot of natural science knowledge
Analysis: bicycle from the structure is a combination of simple machinery, driving the application of mechanical balance principle, so can walk
Application of natural science knowledge:
(1) the handlebar is a labor-saving lever when it rotates. When the power arm is larger than the resistance arm, it can save labor
(2) the brake is a lever in use, which can save labor when the power arm is larger than the resistance arm
(3) the pedal and the big flywheel, the small flywheel and the rear wheel constitute the wheel axle device. When the power acts on the wheel, it can save labor, but it works on the shaft
2. Rubber handle steel wire pliers. The physical knowledge we have learned is applied in its design and use. Please point out the physical knowledge on which it is based
The steel wire pliers are made by using the lever principle of labor saving
When the force is the same, the area is small, which can increase the pressure to cut the wire
The whole Tong is a labor-saving lever, which can save labor
3 rubber handle, surface concave convex pattern, can increase beneficial friction
The handle is insulating plastic, which can prevent electric shock
How do simple machines change our lives? The working principles and concepts of levers and pulley blocks,
And add personal opinion, evaluation, speculation
（1） Lever 1. Definition (1) lever: a hard rod that can rotate around a fixed point under the action of force. This hard rod is a lever. (2) fulcrum: the point that the lever rotates around. (3) power: the force that makes the lever rotate. (4) resistance: the force that prevents the lever from rotating. (5) power arm: the distance from fulcrum to dynamic action line
RELATED INFORMATIONS
- 1. Archimedes's famous saying, as long as we give him a fulcrum on the earth, he can pry up the earth. What's the reason
- 2. Archimedes, a famous ancient Greek scholar, once said, "if you give me a lever and a fulcrum, I can pry the earth." Now let's make a hypothesis that C is the fulcrum, and the lever can rotate around C. We put the earth at point B. if the ratio of the power arm AC and the resistance arm BC of the lever is 5:1, and we want to lift the earth up 10 cm, how many m should we press the A end of the lever down?
- 3. When to use Archimedes theorem to calculate
- 4. Where is the insulating paint scraped away from the resistance wire on the rheostat? Why?
- 5. 1000 ohm = - megaohm, the structure of sliding rheostat -, -, -, -, -, -
- 6. How to judge whether sliding rheostat is current limiting connection or partial compression connection
- 7. What do you think of the circuit diagram of the sliding rheostat? What is the current direction? What is the physical diagram? Why do you want to connect three terminals? What's the current direction? What's the physical picture? Why do you want to connect three terminals? I'm not sure!
- 8. Marxist philosophy is the philosophical foundation of the theory of building socialism with Chinese characteristics
- 9. The relationship among the theoretical system and system of the socialist road with Chinese characteristics
- 10. What is the connotation of the scientific outlook on development
- 11. Please explain the working principle of the movable pulley
- 12. Solving the labor saving principle of moving pulley
- 13. Schematic diagram of forceps force lever Why is forceps a hard lever? Why is the fulcrum the top? Please help draw the diagram of the forced lever and explain it in detail
- 14. How to draw physical lever diagram
- 15. Push up is a common basic exercise. Xiaoming weighs 600N. He does 30 push ups in 1min. Every time he does it, his shoulder rises 50cm. Xiaoming's body is a lever, and O is a key If the area of each palm is 0.016 M & sup2;, calculate the pressure of both hands on the ground and the work done by Xiaoming in 3.1 Min. 4
- 16. Why is Archimedes's lever principle the same type of shovel, what is the shovel?
- 17. Briefly talk about the similarities and differences of the use of lever principle between pliers and guillotine
- 18. Hang two groups of hook codes on both sides of the lever, adjust the number of hook codes or the position on the lever, so that the lever is balanced in the horizontal position. What is the purpose? Record___ 、___ 、____ 、______ Then hang a group of hook codes on the same side of the spring dynamometer, and the spring dynamometer should be pulled vertically upward for the purpose of? In use__________ The fixed pulley is called the fixed pulley_____ But you can____________ And change the direction of tension
- 19. In the experiment of studying lever balance, the nuts at both ends of the lever should be adjusted so that the lever is balanced in its original position. At this time, when the lever is still balanced in its original position after the two ends of the scale are hooked, the distance from the point of action of the force to the fulcrum is equal to that of the force----
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