Knowledge of physical levers, knowledge of the principles of physical levers

According to the shape of the pry usually used, the resistance arm, that is, the part of the iron part of the pry is about l2=5cm, and the power arm, that is, the handle of the pry is about l1=50cm, so it is obtained by f1*l1=f2*l2.

f1 = 150 N.

I haven't used a nail pry for a long time.,The handle is not 50cm.,I can't remember clearly.,But,No.50,There's also 40.,Anyway, it's an estimate.,The error can be bigger.。

If it is based on** Do you want to measure the length of the two arms and then calculate?

Lever. Definition: A hard rod that rotates around a fixed point under the action of force is called a lever.

NOTE: The lever can be straight or curved, and the shape is arbitrary.

In some cases, the lever can be turned around to help determine the pivot point. Such as: fishing rods, shovels.

Five elements - a schematic diagram of the composition lever.

Fulcrum: The point at which the lever turns. With the letter o

Denote. Power: The force that makes a lever turn. with letters. f1 indication.

Resistance: The force that prevents the lever from turning. with letters. f2.

Power arm: The distance from the fulcrum to the line of action of the power. It is denoted by the letter L1.

Resistance arm: The distance from the fulcrum to the line of action of resistance. It is denoted by the letter L2.

Equilibrium conditions for studying leverage:

The equilibrium conditions (or principle of leverage) for leverage are:

Motivation Power Arm Resistance Resistance Arm The formula f1l1=f2l2 can also be written as: f1

f2=l2l1

4. Application: Name. Knot. Frame.

Special. Attack. Special. Dot.

Application examples: Save labour.

Lever. Power arm.

Greater than. Resistance arm.

Labor-saving and distance-consuming.

Crowbars, guillotines, movable pulleys, axles, claw hammers, wire cutters, trolleys, flower shears.

Laborious. Lever.

Power arm. Less than.

Resistance arm. Laborious.

Save distance. Sewing machine pedals, booms.

Human forearms, barber scissors, fishing rods.

Equiarm. Lever.

The power arm is equal to the resistance arm.

No effort. Effortlessly.

Balances, fixed pulleys. 5. Pulleys.

Fixed pulley: Definition: A pulley with a fixed shaft in the middle.

Essence: The essence of the fixed pulley is: equal arm lever.

Features: The use of fixed pulleys can not save effort but can change the direction of power.

Movable Pulley: Definition: A pulley that moves with a heavy object.

Essence: The essence of the movable pulley is: the power arm is twice that of the resistance arm.

Labor-saving leverage.

Features: The use of movable pulleys can save half of the force, but it cannot change the direction of power.

Pulley block. Definition: fixed pulley and movable pulley are combined to form a pulley group.

Features: The use of pulley block can not only save effort but also change the direction of power.

According to the lever equilibrium condition, f1l1=f2l2, and the balance is an equal arm lever, l1=l2, so f1=f2, that is, the power is equal to the resistance, the gravity on both sides of the pallet is equal, according to g=mg, when g is certain, m is equal, so the mass of the right disk weight is equal to the mass of the left disk object.

The knowledge points of the principle of physical lever are as follows:

1) Hang equal weights at the ends of the weightless rod at an equal distance from the fulcrum, and they will balance.

2) Hang unequal weights at equal distances from the fulcrum at both ends of the weightless rod, and the heavier end will tilt downward.

3) Hang the two ends of the weightless rod at an unequal distance from the fulcrum, and the far end will tilt downward.

4) The action of one weight can be replaced by the action of several evenly distributed weights, as long as the position of the center of gravity remains the same. Conversely, several evenly distributed weights can be replaced by one that hangs at their center of gravity.

5) The center of gravity of similar figures is distributed in a similar way.

6) Levers can be divided into labor-saving levers, labor-saving levers and equal-arm levers, and there is no one kind of lever that saves both distance and effort.

Conceptual Analysis of Leverage Principle:

When using a lever, in order to save effort, you should use a lever that is longer than the resistance arm; If you want to save distance, you should use a lever that is shorter than the resistance arm. Therefore, the use of levers can save effort and distance. However, if you want to save effort, you must move more distance; If you want to move less distance, you have to work harder.

It is impossible to achieve it with less effort and less distance. The fulcrum of the lever does not have to be in the middle, and the system that satisfies the following three points is basically the lever: the fulcrum, the force point, and the force point.

Both levers are useful, but where they need to be used to evaluate whether they need to save effort or range of motion. There is also something called an axle, which can also be used as a lever, but the performance may sometimes be accompanied by a rotation calculation.

The ancient Greek scientist Archimedes has such a famous saying that has been passed down through the ages: "If you give me a fulcrum, you can pry up the earth" This sentence is not only an inspiring aphorism, but also has a strict scientific basis.

Summary of the knowledge of the principle of lever and its balance in physics.

Leverage knowledge points.

Definition of lever: A hard rod that rotates around a fixed point under the action of force is called a lever.

NOTE: The lever can be straight or curved, and the shape is arbitrary.

In some cases, the lever can be turned around to help determine the pivot point. Such as: fishing rods, shovels.

Lever classification: labor-saving levers, labor-saving levers, and equal-arm levers.

The five elements of leverage are mainly as follows:

Fulcrum: The point at which the lever turns. It is denoted by the letter O.

Power: The force that makes a lever turn. It is denoted by the letter F1.

Resistance: The force that prevents the lever from turning. It is denoted by the letter F2.

Explanation: Power and resistance are both forces on the lever, so the action point is on the lever. The direction of the momentum and resistance is not necessarily the opposite, but they make the rotation of the lever in the opposite direction. ）

Power arm: The distance from the fulcrum to the line of action of the power. It is denoted by the letter L1.

Resistance arm: The distance from the fulcrum to the line of action of resistance. It is denoted by the letter L2.

Do you know how leverage works? Iron rods can easily pry open boulders, using the principle of leverage to the extreme.

The physical and chemical bar rules are the abbreviations of the physical and chemical bar rules that students often have.

Leverage rule: The relationship between the quantities of substances in the various parts of the system calculated by the mass balance. Let the molecular fraction of a component in the system be, if the system is divided into two parts with molecular fractions of x1 and x2, then the following relationship must be observed between their molar numbers n1 and n2:

n1 n2=(x2-x) (x-x1), this relationship is like the calculation formula of levers with x as the fulcrum and x2-x and x-x1 as the arm length, hence the name. If the weight fraction is used, the weight ratio is obtained. The physical and chemical bar rules are the abbreviations of the physical and chemical bar rules that students often have.

Leverage rule: The relationship between the quantities of substances in the various parts of the system calculated by the mass balance. Let the molecular fraction of a component in the system be, if the system is divided into two parts with molecular fractions of x1 and x2, then the following relationship must be observed between their molar numbers n1 and n2:

n1 n2=(x2-x) (x-x1), this relationship is like the calculation formula of levers with x as the fulcrum and x2-x and x-x1 as the arm length, hence the name. If the weight fraction is used, the weight ratio is obtained.