How to bend the lever to find the strength of the arm, etc., the distance of the power arm of the th

The perpendicular line between the direction of the force and the transmission point is the point.

1. Leverage 1) The basic concept of leverage.

A hard rod that can rotate around a fixed point under the action of force is called a lever.

Five terms for leverage: Fulcrum: The point around which the lever rotates (o); Power:

the force that turns the lever (f1); Resistance: The force that prevents the lever from turning (f2); Power arm: the distance from the fulcrum to the line of action of the power (L1); Resistance Arm:

The distance (L2) from the fulcrum to the resistance action line.

2) Conditions for Leverage Balance.

Power Power Arm = Resistance Resistance Arm, this equilibrium condition is the principle of lever discovered by Archimedes.

3) Three types of leverage:

Labor-saving leverage: L1>L2, F1F2 in balance. It is characterized by laborious, but saves distance. (such as fishing rods, barber scissors, etc.).

Equal arm lever: l1 = l2, f1 = f2 when balanced. It is characterized by neither effortless nor labor. (e.g. balances).

2. Buoyancy 1) Buoyancy.

The force by which an object immersed in a liquid or gas is held upwards by a liquid or gas is called buoyancy. Buoyancy occurs because an object immersed in a liquid (or gas) is subjected to the difference between the upward and downward pressure of the liquid (or gas) on it.

The buoyant force is applied to a liquid (or gas), and buoyancy is an elastic force.

2) Archimedes' principle.

An object immersed in a liquid experiences an upward buoyant force equal to the gravitational force expelled by the liquid it displaces. Expression: f float = g row = liquid v row g (Archimedes' principle also applies to gases).

From this, it can be concluded that the two factors that affect the magnitude of buoyancy are the density of the liquid and the volume of the liquid discharged by the object.

3) Calculation method of buoyancy.

Archimedes' principle: F float = g discharge = liquid v discharge g (also applicable to gases).

2. Force balance: F float = g matter (suitable for floating, levitation).

Multi-force balance: f float = g f (this is the buoyancy measured with a spring dynamometer).

Differential pressure method: F float = F up - F down (not commonly used).

4) Measurement of buoyancy.

Common method: measure the gravity g of the object with a spring dynamometer, immerse the object in the liquid and read out the indication f of the spring dynamometer, then the buoyancy of the object immersed in the liquid is: f float = g f.

Measuring V row (graduated cylinder) method: Measure V row, and calculate the buoyancy with F float = G row = liquid V row G.

5) The float and sink conditions of the object.

The float and sink of an object submerged in a liquid is determined by the relationship between the gravitational force and the amount of buoyancy it is subjected to. When gravity is greater than buoyancy, the object sinks; When gravity is equal to buoyancy, the object is suspended; When the gravitational force is less than the buoyant force, the object floats upward.

6) Utilization of buoyancy.

Steamer: The hollow method is used to increase the available buoyancy, so that the ship can float on the water. The size of the ship is expressed in terms of its displacement - the mass of the water discharged when fully loaded.

Submarines: Submarines float and sink by changing their own gravity.

Balloons and airships: both work using the buoyancy of air. The lifting of balloons and airships is mainly achieved by changing the volume of the airbag and thus changing the buoyancy experienced by itself.

The distance of the reading power arm of the three types of levers:

1) Labor-saving lever: the power arm is larger than the resistance arm, and the power is less than the resistance; This kind of lever saves effort and takes a distance

2) Laborious lever: the power arm is smaller than the resistance arm, and the power is greater than the resistance; This kind of lever takes the effort of the yard and saves the distance

3) Equal arm lever: the power arm is equal to the resistance arm, and the power is equal to the resistance of the boy; This kind of leverage, which is neither labor-saving nor labor-intensive

Lever. Definition: 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.

Five elements - a schematic diagram of the composition lever.

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.

Draw the force arm method: one to find the fulcrum, two to draw the line, three to the distance, four labels.

Find the fulcrum o; draw the action line of the force (dashed line); Draw the force arm (dashed line, the line of action of the vertical force through the fulcrum is the perpendicular line); Standard force arm (braces).

Equilibrium conditions of the lever: power power arm = resistance resistance arm.

Formula: F1 L1 = F2 L2 Variant: F1: F2=L1: L2 The power arm is several times that of the resistance arm, then the power is a fraction of the drag difference.

A lever that is stationary or rotates at a constant speed is called lever balancing.

The straight line of the rock along the direction of the force through the point of application of the force is called the line of action of the force.

The vertical distance L1 from the fulcrum O to the line of action of the power F1 is called the power arm.

The vertical distance L2 from the fulcrum O to the line of action of resistance F2 is called the resistance arm.

Condition of lever equilibrium (literal expression): power power arm = resistance resistance arm.

Power Arm Power = Resistance Filial Piety Arm Resistance, that is, L1 F1 = L2 F2, which can evolve into F1 F2 = L1 L2 The balance of the lever is not only related to power and resistance, but also related to the point of action of the force and the direction of action of the force.

If the power arm is n times that of the resistance arm, then the power is 1 n of the resistance"Big head sinks"

The longer the power arm, the less effort, and the longer the resistance arm, the more laborious.

Labor-saving leverage fee distance; Laborious lever saves distance.

The equal-arm lever is neither labor-saving nor labor-intensive. It can be used for weighing. In mechanics, the typical lever is placement.

Hello landlord

I watched it for a long time and was not stunned, but I didn't understand what the focus of the first floor was......I don't know if the landlord understands it, so as far as I understand it, tell the landlord how to do the lever arm and its minimum force, I call it f1, and the minimum force to draw is f2

1. Find the fulcrum of the lever and find the point of action of F1.

2. Under normal circumstances, the extension line of F1 should be drawn, and the perpendicular line of F1 should be made through the fulcrum, then this perpendicular line is the force arm of this force (that is, the shortest distance from the force to the fulcrum - pay attention to the line segment perpendicular to the force).

3. To make the minimum force, first understand that the longer the force arm, the smaller the force required, so it is necessary to find the point farthest from the fulcrum on the diagram. Then draw the equilibrium force f2 of f1 at this point, which is usually a force parallel to f1.

If f1 and f2 are on the same side of the fulcrum, then f1 and f2 will be in opposite directions, and if f1 and f2 are on both sides of the fulcrum, then the two forces will be in the same direction.

I drew the first two of the drawings given on the first floor.

I hope it will help you, if there is something inappropriate, please point out a certain Schrödinger's cat.

There are two questions to your question:

1. The following issues should be paid attention to on how to make a lever arm:

First of all, it is necessary to find the position of the fulcrum o, and then find out the line of action of the force; Immediately after the perpendicular line of action of the force (which can be extended forward or backward as needed) through the fulcrum o force, the length of this perpendicular segment is the arm of the force.

2. As for how to make the minimum force on the lever, I told the students a dead concept in my lecture: if you want to have the smallest force, you must use the line from the fulcrum to the line of action of the force as the force arm.

Because the arm and the line of action of the force are perpendicular to each other, the position of this minimum force is in a straight line perpendicular to the arm at the point of action of the excess force.

The next step is to determine the direction of the force. According to the direction of Lide, the lever can be divided into two categories: one is that the fulcrum is at the end of the lever, and the two forces are on the same side of the fulcrum, and the direction of the two forces is on the opposite side of the lever, otherwise the lever will rotate around the fulcrum (while general physics drawing problems require the lever to be balanced at a certain position); The other type is that the fulcrum is in the middle of the lever (not necessarily in the middle), and the two forces are on the opposite side of the fulcrum, and the direction of the two forces is on the same side of the lever, otherwise the lever will also rotate around the fulcrum.

This solves your second problem.

In order to make you understand better, I seem a little wordy, here I will not give you a diagram, only give you theoretical knowledge, as long as you read my description, I am sure that you can make a diagram. I hope it can solve the doubts in your heart! In the meantime, I wish you progress!

Hello! The line of action of the force and the line of action of the resistance may be in the same direction or in opposite directions. If you draw a diagram where the two forces are at opposite ends of the lever and are in opposite directions, then the lever can be rotated, so it is a wrong ......

Think for yourself when you make a picture. Think about the direction of two forces. Especially the direction of resistance!! For example, if a claw hammer pulls a nail upward, the force on the nail goes up, and the resistance goes down.

Minimum force plotting. Fulcrum force point connecting a line, over the force point, do a perpendicular line! Of course, to pay attention to the direction!

See references for details.

Secondary: The arm is the vertical distance from the fulcrum to the direction of the force, which is to draw the direction of your force as a straight line, and then draw the perpendicular line of this straight line through the fulcrum. Draw a picture to know which direction is the most effortless.

University: Moment m (vector) = r (vector) f (vector). The r vector is the vector of the point of action of the rotational axis pointing to the force.

Because force is a vector, in the lever system, the force arm refers to the distance between the force and the fulcrum, as shown in the figure, the lever with O as the fulcrum at the end of point A, there is a force F, according to the definition of the force arm, the force arm of the O point is the distance from the O point to F, that is, the perpendicular line of the O point is f, and the length of the line segment od when the vertical foot is d

As can be seen from the figure, OD is equivalent to a right-angled side of the right-angled triangle ODA, in this triangle, OD is always less than OA, only when F is perpendicular to OA, OD=OA, OD reaches the maximum, that is, the force arm of F to the point O reaches the maximum.

1.Draw the force arm formula: one to find the point (fulcrum), the second to draw the line (the line of force, which can be extended in both directions as needed), from the point to the line as a perpendicular line (from the fulcrum to the force line as a perpendicular line), the fulcrum is bracketed.

Find the fulcrum o; draw the action line of the force (dashed line); Draw the force arm (dashed line, the line of action of the vertical force through the fulcrum is the perpendicular line); the distance between the pivot point and the perpendicular foot (solid line, double arrow, or curly braces); Standard force arm (braces).

Drawing skills. The way to test whether the drawn force is in the correct direction is to see if the force and resistance have the opposite effect of turning the lever. The direction of the momentum and resistance is not necessarily the opposite, but they must make the lever turn in the opposite direction:

When the power and resistance are on both sides of the fulcrum, they are in roughly the same direction; When the momentum, resistance is on the fulcrum side, they are in roughly opposite directions. (abbreviated as ipsilateral isodirection, opposite lateral isodirection).

2.Least power problem when lever balanced: In this type of problem, the resistance arm is a certain value, and in order to minimize the power, the power arm must be maximized. To make the power arm the maximum need to do:

If the dynamic application point has been given, then the line from the fulcrum to the dynamic application point is the longest force arm.

If the dynamic action point is not determined, the point farthest from the fulcrum on the lever is selected as the dynamic action point, and the force arm made by the connection between the fulcrum and the dynamic action line is the longest force arm.