What are some good teaching methods for the 9th grade physics lever section? Seek advice

Analyze the five elements of the lever with physical objects, especially the force arm (in the lever, it is equivalent to the point and direction of the three elements of the force), and do a good job in the experiment of the balance condition of the lever.

Hehe, this thing is so simple, five elements.

Focus on mastering the balance conditions of the lever, and at the same time will find the point of action of the force, and will draw the line of action of the force!

Draw the power arm and the resistance arm:

1.Determine the pivot point of leverage.

2.Do the line of action of the force.

3.From the fulcrum to the line of action of the force to make a perpendicular segment, this perpendicular segment is the force arm.

I think there will be a lot of charts if you learn leverage. Then the first thing to do is to learn how to analyze graphs.

The most basic thing is to determine the fulcrum of the power resistance and the power arm resistance arm. Once you've got all of this in mind, it's easy to learn leverage. But I think the hardest thing to determine is the pivot and resistance.

The determination of fulcrums and resistance still depends on the observation of life in some aspects. Just take it and do a little more practice.

Again, you have to learn to distinguish between labor-saving levers and labor-saving levers, the power-saving lever has a larger power arm than the resistance arm, and the labor-saving lever is the power-saving arm smaller than the resistance arm. If you want to determine which is the labor-saving lever and which is the labor-saving lever, you must first determine the fulcrum, the power arm and the resistance arm. In the end, if you do more questions and understand these five elements, find these five important elements to come out, and you will have a good foundation for leverage.

In addition, the basic structure of the axle.

The outside is the wheel, the inside is the shaft, when acting on the wheel, the axle is a labor-saving lever, when acting on the shaft, it is a labor-saving lever. Junior axles don't need to be too complicated to master, just understand the basics. You can analyze the example diagram.

If you still have questions, please feel free to ask them again!

Junior High School 9th Grade Physics Lever Lesson Plan Design:Preparation for teaching

Teaching Objectives: 1.Knowledge & Skills.

1) Recognize levers, know the concepts of fulcrum, power, resistance, power arm, resistance arm, etc.

2) Know the equilibrium conditions of leverage and some applications.

3) Leverage can be identified from common tools and simple machines.

2.Process & Methodology.

1) Go through the process of drawing a schematic diagram of a lever and experience the method of scientific abstraction.

2) Observe and operate the lever and experience the role of the lever.

3) The process of going through the ** leverage equilibrium condition. Learn the general method of analyzing experimental phenomena, finding patterns between data, and deriving experimental conclusions from them.

3.Emotions, Attitudes and Values (1) Care about life, production, and the application of auspicious spring levers in natural phenomena.

2) Be willing to discover and analyze various levers in the surrounding life, and have the awareness of using leverage to facilitate their own work.

3) There must be a spirit of cooperation in understanding science**.

Teaching is a major and difficult task.

Focus: Awareness of leverage, equilibrium conditions for leverage.

Difficulty: fulcrum, force arm.

Teaching tools. Scissors, pliers, sticks, etc.

Teaching process

Process design for teaching and learning.

The concept of leverage is introduced through examples of simple machines in everyday life.

One. Leverage: (concept).

A stiff rod that rotates around a fixed point.

1.Fulcrum (o): The point around which the lever turns.

2.Power (f1): The force that makes the bar rotate like a rod.

3.Resistance (f2): The force that prevents the lever from turning.

4.Power arm (1): The distance from the fulcrum to the line of action.

5.Resistance arm (2): The distance from the fulcrum to the line of action of resistance.

IILeverage Balance:

When the lever rotates at a static or constant speed under the action of power or resistance, it is called lever balance.

Students work in groups to experiment: Equilibrium conditions for leverage. Instruct students to conduct experiments.

Based on the results of the experiments, the discussion drew conclusions.

Three. Equilibrium conditions for leverage:

f1l1=f2l2

4. Classification of leverage:

Fifth, be cautious and patient. Application of leverage:

1.Labor-saving levers: L1>L2, wire cutters, bottle openers, nail clippers, screwdrivers, etc.

2.Laborious leverage: L1

1. Definitions: The core of a hard rod that rotates around a fixed point under the action of force is quietly called a lever.

Description: 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.

2. Five elements - a schematic diagram of the composition lever.

Fulcrum: The point at which the lever rotates around the slag and is indicated by the letter O.

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

Resistance: The force that prevents the lever from turning, denoted by the letter 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.

3. Study the equilibrium conditions of leverage:

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

Power x power arm = resistance x resistance arm, written as the formula f1l1=f2l2 can also be written as: f1 f2=l2 l1

Fourth, the application:

Name Structure.

Characteristics Examples of applications.

Save labour. Lever power arm.

Greater than. Resistance arm labor-saving

Fee distance Crowbars, guillotines, movable pulleys, axles, claw hammers, wire cutters, trolleys, flower branch scissors.

Laborious. Lever power arm.

Less than. Resistance arm Laborious

Save distance sewing machine pedals, crane arms.

Human forearms, barber scissors, fishing rods.

Equiarm. The lever power arm is equal to the resistance arm without effort.

Effortless balances, fixed pulleys.

5. Pulleys

1. 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.

2. Movable pulley:

Definition: A pulley that moves with a tardiness.

Essence: The essence of the movable pulley is: the power arm is a labor-saving lever twice that of the resistance arm.

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

3. 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.

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.

Description: 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.

General steps for lever drawing:

1) Find the fulcrum o; (Note: Be sure to mark the letter o!) ）；

2) draw the line of action of the force; (Note: The size, direction, and point of action of the force should be marked with the letters F1 or F2.) If the line of action of the force needs to be extended, the extension line part is indicated by a dashed line);

3) Draw the arm of the force; (The perpendicular line of the line of action of the force from the fulcrum.) Note: Perpendicular lines are indicated by dashed lines and marked with vertical symbols at the perpendicular feet);

4) mark out the force arm; (The arm is the distance from the fulcrum to the vertical foot, marked with curly braces and marked with L1 or L2);

I hope it helps you, and if you have any questions, you can ask them

I wish you progress in your studies and go to the next level! (*

If so, the principles of drawing are: 1. Find out the position of the fulcrum; 2. Clarify the position of the force (power or resistance) action line; 3. The perpendicular line of the action line of the fulcrum as a force, and the distance of the perpendicular line segment is the force arm. 4. Mark the corresponding letters, vertical symbols, braces, etc.

The first thing you should do is understand what the distance from a point to a line is.

The uniform center of gravity is in the middle of AB, that is, at the distance B or meters, so how to determine the fulcrum, because the cement pier is thick, according to the situation, this fulcrum should be determined on the outer edge of the mud pier with a wooden plank protruding, that is, the force arm of gravity is 4

This is according to the leverage balance conditions.

G Person*L1 G-Wood*L2

m human * g * l1 = m wood * g * l2

De: L1 4m

Obviously, this is beyond the length of the plank, so the furthest is to the end of the plank, which is the cement pier.

Of course, because there is no diagram, I probably imagined the diagram according to the question. It should be what I think, and if it's not the standard answer, then it's possible that I'm wrong. But that's certainly the way the train of thought goes.

As shown in the figure below, the center of gravity of the BC (C is the right point of the pier) section is at the midpoint O, BO=(4+, the center of gravity of the right part of the pier is on the right side of the C point (, the maximum distance between the person is C point L, according to the lever balance conditions: GBC * person * L, G = MG, after bringing in the values, it can be found: L = 4M

Wow, we're just learning about power.

The principle of leverage is also known as the "leverage equilibrium condition". For a lever to be balanced, the magnitude of the two forces acting on the lever (the power point, the fulcrum, and the resistance point) is inversely proportional to their arms. Power Power Arm = Resistance Resistance arm, expressed algebraically as f

l1=w•l2。where F represents the power, L1 represents the power arm, W represents the resistance, and L2 represents the resistance arm. From the above formula, it can be seen that in order to balance the lever, the power arm is several times that of the resistance arm, and the power is a fraction of the resistance.

1.Labor-saving levers: L1> L2, F1, labor-saving, distance-saving. Such as claw hammers and guillotines used to pull nails.

2 Laborious leverage:

L1 L2, F1 F2, laborious, distance-saving, such as fishing rods, tweezers, etc.

3 Equal Arm Lever:

L1 L2, F1 F2, neither labor-saving nor labor-intensive, and do not move much distance, such as balances, fixed pulleys, etc.