What is a Simple Machine?
Simple machinery is the most basic machinery and an important part of machinery. Simple machinery is the basic mechanical element of human force. In the earliest great discoveries of human beings, the mastery of tools, fire, and language made humans finally get rid of ordinary animals. Simple machinery is the wisdom of man using mechanical tools in transforming nature and is an important object of Newtonian mechanics (vector mechanics).
- Chinese name
- Simple machinery
- Simple machinery is the most basic machinery and an important part of machinery. Simple machinery is the basic mechanical element of human force. In the earliest great discoveries of human beings, the mastery of tools, fire, and language made humans finally get rid of ordinary animals. Simple machinery is the wisdom of man using mechanical tools in transforming nature and is an important object of Newtonian mechanics (vector mechanics).
Simple mechanical formula
W Simple machinery W useful
W Simple Machinery W
W Simple Machinery W Extra
Simple mechanical terms explained
Simple machine simple machine
- Any device that can change the magnitude and direction of the force is collectively called "mechanical". The use of machinery can both reduce physical labor and improve work efficiency. There are many types of machinery and they are more complicated. According to Galileo's tips, people have tried to break down all machinery into several simple machines. In fact, this is very difficult. Usually, the following machines are used as the basis for research. For example, levers, pulleys, axles, gears, bevels, spirals, splits, etc. The first four simple machines are deformations of the lever, so they are called "simple lever machines." The latter three are deformations of inclined planes, so they are called "simple inclined planes". No matter which type of simple machine is used, the general law of the machine must be followed-the principle of work.
Simple mechanical lever
- A simple machine made of a rigid material whose shape is a straight or curved rod that can rotate around a fixed point or a certain axis under the action of external forces. There are fulcrum points (represented by O), dynamic (F) action points, and resistance (W) action points. The fixed rotation axis of the lever is commonly referred to as the "fulcrum". The vertical distance from the rotation axis to the dynamic action line is called "power arm ", The vertical distance from the axis of rotation to the line of resistance action is called the" resistance arm ". The above are the three points and two arms usually mentioned. Because the positions of the three points on the lever are different, different force effects are produced.
Simple mechanical lever principle
- Also known as "leverage conditions." To balance the lever, the two forces (power and resistance) acting on the lever are inversely proportional to their force arms. Power × power arm = resistance × resistance arm, expressed by algebraic formula as
- F1L1 = F2L2
- Simple machinery
Simple mechanical power
- Any machine, whether simple or complicated, always receives two kinds of forces when it works. One is the force that pushes the machine. It is called "power". The power is the force that rotates the lever. The other is the force that hinders the movement of the machine called "resistance." Resistance is the force that prevents the lever from turning. Power can be manpower, animal power, wind power, electricity, water power, steam pressure, etc. In addition to the useful resistance we have to overcome, there are some unavoidable useless resistance.
Simple mechanical action line
- The straight line drawn by the point of application of the force in the direction of the force is called the "line of action of the force".
Simple mechanical power arm
- The vertical distance from the fulcrum to the line of action of the force is called the "force distance". The vertical distance L1 from the fulcrum to the line of action of power F1 is called a "power arm"; the vertical distance L2 from the fulcrum to the line of action of resistance F2 is called a "resistance arm". If the long rod length from the power point to the fulcrum is used as the power arm, or the long rod length from the resistance point to the fulcrum is used as the resistance arm, this understanding is wrong. This is due to the unclear understanding of the concepts of the power arm and the resistance arm.
Simple mechanical resistance arm
- See Power Arm.
Simple mechanical rotation axis
- Rotation is a common movement. When an object rotates, its points make circular movements. The centers of these circles are on the same straight line. This straight line is called the "rotation axis". Doors, windows, grinding wheels, rotors of electric motors, etc. all have fixed rotating shafts, which can only rotate but not translate. Several forces act on the object, and their rotation on the object depends on the algebraic sum of their moments. If the algebraic sum of moments is equal to zero, the object will rotate at a constant speed using the original angular velocity or remain stationary.
Simple mechanical three types of leverage
- There are two ways to classify leverage. The first is divided by the position of the fulcrum, resistance point and power point; the other is distinguished by labor-saving or labor-intensive. No matter how you divide it, you can't do without labor, labor, and equal arms.
- Simple machinery
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Simple machinery mechanical efficiency
- A physical quantity that indicates the degree of effort saving of a machine. Although machinery can never save effort, it can save effort. The force that makes a machine work is called "power" (F), and the force that hinders the work of a machine is called "resistance" (P). The purpose of using machinery is to balance resistance with very little power. The so-called mechanical efficiency (A) is the ratio of the useful resistance (P) of the machine to the power (F).
- When the mechanical efficiency is less than 1, labor-saving and time-consuming, for example, unicycles, pliers, screwdrivers, labor-saving levers, etc. are all labor-saving machinery. When the mechanical efficiency = 1, no effort or effort is required. For example, physical nature. When the mechanical efficiency is less than 1, it may be labor-saving and time-saving, such as bamboo clips and fire tongs. The mechanical benefit is determined by the actual resistance and power measured. Due to the different conditions of mechanical lubrication, there are differences in overcoming the same useful resistance. The mechanical lubrication is not good, the useless resistance is large, the power is also large, and the mechanical efficiency is small; the mechanical lubrication is good, the useless resistance is small, the power is small, and the mechanical efficiency is large. The newly produced machines need to run in. It takes a while for the car to leave the factory to reduce its frictional resistance. But the machine is outdated and the parts are worn, which will increase the resistance.
Application of simple mechanical lever
- Different types of leverage have different characteristics and uses. After mastering the principle of leverage, you can consciously choose different types of leverage to use as needed. It should be clear: labor-saving lever saves effort but requires more distance, labor-consuming lever takes effort but saves distance, equal-arm lever does not save effort and distance, and there is no lever that saves effort and distance. Whether some levers save effort or distance is not constant. Depending on usage, it will change from labor saving to distance saving. For example, the process of loading soil with a shovel will change. The fulcrum is between the power point and the resistance point during shovel, and the fulcrum is between the fulcrum point and the resistance point during soil loading. For this reason, there are a few points to note when using leverage:
- 1. When solving the problem of leverage, you must draw a schematic diagram according to the intent, and mark the fulcrum, dynamic action line and resistance action line of the lever on the diagram. At the same time, the size of the power arm and the resistance arm are marked with line segments, and the equations are listed according to the leverage balance conditions for calculation.
- 2. The arm is an important concept. The arm is the vertical distance from the fulcrum to the line of action of the force. Do not interpret the arm as the length from the fulcrum to the point of action of the force. Power and resistance are both forces acting on the same lever, not forces acting on weights or other objects.
- 3. Method of drawing the lever diagram:
- (1) Draw the lever: use a thick straight line to represent a straight lever, and use a curved thick line to represent a curved lever.
- (2) Find the fulcrum when the lever rotates, and use the arrow next to the fulcrum to indicate the direction of the lever's rotation.
- (3) Determine the direction of power and resistance based on the direction of rotation. The points of action of power and resistance should be drawn on the lever and can be represented by a schematic diagram of force.
- (4) The extension of the line of action of the force and the arm are indicated by a dashed line.
- 4. The balance condition of the lever is applicable to any balance position. The so-called balance of the lever means that the lever does not rotate or rotates at a constant speed.
Simple mechanical steelyard
- It is a measuring tool for measuring the mass of an object. It is manufactured based on the principle of lever balance, using Tinew as the axis of rotation. Steelyards are mainly composed of weighing rods, scales, hooks (or weighing pans), etc. As shown in Figure 1-23. G represents the gravity of the steelyard, and point B is its focus.
- Point A is the "fixing star" of the steelyard. After adding W to the scale hook, move scale from point A to A '
- The position of the scale A 'corresponding to the force G. The steelyard is a measuring tool invented and used by the working people in our country. The old scale was measured in kilograms and two, and the modern scale was measured in kilograms.
Simple mechanical moment
- Also called "torque" is a physical quantity that means that when a force acts on an object, the object rotates or changes the state of rotation. Moments are vectors. The magnitude of the moment is equal to the product of the force and the vertical distance from the axis of rotation to the line of action of the force. If the force on the object is not in the plane perpendicular to the rotation axis O, the force must be decomposed into two component forces: one component force is parallel to the rotation axis; the other component force is in the plane of rotation. Only the component force in the rotation plane can change the rotation state of the object. Therefore, in the calculation of the moment equal to the product of the force and the arm, it should be understood that the force is the component force in the plane of rotation of its point of action. If this is on the line of force, the moment is zero. If several forces are acting on an object at the same time, the resultant moment is the algebraic sum of all partial moments. For a balanced object, the sum of the clockwise moments is equal to the sum of the counterclockwise moments. In the International System of Units, the unit of torque is meter Newton. Its direction is determined by the right-hand spiral rule. At the middle school level, because only the balance of an object with a fixed axis is studied, there are only two types of steering moments. It is required that the torque of the object rotating counterclockwise is positive, and the torque of rotating the object clockwise is negative. The larger the torque, the more obvious the effect of changing the rotation state of the object. When pushing the door with the same force, the farther the point of action of the force is from the rotation axis and the direction is perpendicular to the door, the larger the force arm is, the more effort is saved in pushing the door.
Simple mechanical couple
- Two forces of equal size and opposite directions, but with lines of action that are not on the same line, are called "force couples." When tapping the thread with both hands or turning the key or faucet by hand, the force applied is often a force couple. It can make an object rotate or change its rotation state. The pair of forces exerted by the driver when turning the steering wheel with both hands is a force couple. The rotation effect of the force couple is determined by the magnitude of the force couple moment. The force couple moment is equal to the product of the magnitude of any one of the forces and the vertical distance (force couple arm) between the two force action lines. As shown in Figure 1-24. If the direction of the acting force F is perpendicular to AB and the length of AB is equal to d, then the moment of force (M) of this force couple is:
- M = ± Fd.
- In the formula, Fd is the magnitude of the force couple moment, and the symbol is used to indicate the turning of the force couple. It is stipulated that the force couple turns counterclockwise to take "+", otherwise it takes "-" (it can also be stipulated that the force couple turns clockwise to take "+", then the force couple turns counterclockwise to take "-"). It should be noted that when the direction of the force in the force couple is not perpendicular to AB, it should be decomposed into vertical components like the moment, and then calculated. The torque of a force couple (ie, the moment of a force couple) is independent of the point around which it is rotated. Because the combined force of the force couple is zero, it cannot make the object move, it can only make the object rotate or change the rotation state of the object.
Simple mechanical force moment
- Abbreviated as "torque of the force couple", also known as "torque of the force couple". A force couple is two equal parallel forces, and their combined moment is equal to the product of one of the parallel forces and the distance between the parallel forces (called the force couple arm). A force couple moment is a vector. The relationship between its direction and the directions of the two forces that make up the force couple follows the right-hand spiral rule. For an object with a fixed axis, the object will rotate around the fixed axis under the action of the force couple; for an object without a fixed axis, the object will rotate around the axis passing through the center of mass under the action of the force couple.
Simple mechanical coupling arm
- The vertical distance between two forces of a force couple. See Figure 1-24.
Simple mechanical axle
- It is a simple mechanism of lever type composed of two wheels with different radii fixed on the same shaft. The larger radius is the wheel, and the smaller radius is the shaft. They are discs in form, but in essence only their diameter or radius plays a mechanical role. Let R be the wheel radius, which is the power arm; r is the shaft radius, which is the resistance arm; O is the fulcrum. When the wheel shaft is rotating at a constant speed, power × wheel radius = resistance × shaft radius, so the larger the difference between the wheel and shaft radii, the more effort is saved. The power of the above formula is expressed by F, and the resistance is expressed by W, which can be written as FR = Wr.
- That is, the use of wheels can save effort. If a heavy object is hung on the wheel, it becomes a laborious axle, but it can save distance. The principle of the axle can also be analyzed by the principle of mechanical work. For each revolution of the wheel shaft, the power work is equal to F × 2R, and the resistance work is equal to W × 2r. Regardless of unnecessary resistance, mechanical
- The hoes, winches, stone mills, steering wheels of automobiles, manual winches, etc., which are common in daily life, are all wheel machinery.
Simple mechanical pulley
- A pulley is a simple mechanism that deforms a lever. It is a wheel that can rotate around the central axis and has grooves around it. When using, select as needed. The pulleys can be divided into fixed pulleys, movable pulleys, pulley groups, and differential pulleys. Some labor-saving, some can change the direction of the force, but can not save effort.
Simple mechanical fixed pulley
- The shaft of the pulley is fixed, it is essentially an equal arm lever. The power arm and the resistance arm are both the radius r of the pulley, according to the principle of leverage Fr1 = Wr2. Its mechanical benefits are
- The direction of the power is changed. If you want to lift the object to a high place, the upward force, such as the fixed pulley, can be used instead, so it is easy to work.
Simple mechanical moving pulley
- A pulley whose axis and weight move together. It is essentially a lever with a power arm twice as large as a resistance arm. According to the principle of leverage balance Wr = F · 2r, its mechanical advantage
- Change the direction of the force. Its direction is consistent with the direction in which the object moves.
Simple mechanical pulley block
- The combination of moving pulley and fixed pulley is called "pulley group". Because the moving pulley can save effort, the fixed pulley can change the direction of the force. If several moving pulleys and fixed pulleys are combined to form a pulley group, the magnitude of the force can be changed, as well as the direction of the force. The ordinary pulley set is composed of an equal number of fixed pulleys and moving pulleys. These pulleys are either located on the same wheel frame (or "wheel"), or they are mounted on the same shaft center next to each other. One end of the rope is fixed on the upper wheel frame, which is equivalent to being tied to a fixed hanging device, and then the rope is passed around each of the lower movable pulley and the upper fixed pulley in turn. At the unrestrained end of the rope, pull it with F force, and the pulled weight is hung on the movable wheel frame. The ropes can be regarded as parallel to each other. When the tension is balanced with the weight, the weight W must be borne by each rope evenly. If there are n fixed pulleys and n movable pulleys,
- When it is moving at a constant speed, the required F force is still the same as above. Therefore, you can save effort when lifting heavy objects. Its transmission ratio is F: W = 1: 2n. Note that when using a pulley set, you can't save effort, you can only save effort, but the effort is based on multi-distance consumption (ie, travel).
- The fixed pulley, the movable pulley and the pulley group analyzed in the foregoing are all conclusions drawn without considering the pulley gravity and the frictional resistance between the pulley and the shaft. However, in actual use, wheel weight and frictional resistance actually exist, so the actual force used is greater.
Simple mechanical differential pulley
- The chain elevator is a pulley block used for lifting. Above is a fixed pulley composed of two disks A and B with different diameters mounted on the same shaft. Below is a moving pulley, which is connected with a fixed pulley above by a cable to form a pulley set. If the radius of the large wheel A is R and the radius of the small wheel B is r, as shown in the figure. When the power F zipper bar makes the large wheel turn once, the power F zipper bar moves down 2R, and the large wheel rolls up the chain 2R. At this time, the small wheel also rotates one round and lowers the chain length 2r. The height of the moving pulley and weight W is 2 (Rr).
- Differential pulley
- Since 2R is greater than (Rr), the mechanical benefit of the differential pulley is greater than 1. If the mechanical benefit is increased, the radius of the two wheels can be increased while the radius difference between the two wheels can be reduced. This machine, also known as the "fairy gourd", is manual and also driven by electricity. The chain is closed. To prevent sliding between the pulley and the chain, teeth on the pulley cooperate with the chain.
Simple mechanical bevel
- A simple machine that can be used to overcome the difficulty of lifting heavy objects vertically. Distance ratio and force ratio both depend on
- Simple machinery
- FL = Gh. The experiment proves that the pulling force F required to pull up the heavy object along the smooth inclined plane is less than the gravity G of the heavy object, that is, the use of the inclined plane can save labor. When the height of the inclined plane is constant, the required pulling force of different inclined planes with different length L is also different: The longer L, the smaller F, the less effort
- The smaller the inclination, the longer the slope, the less effort, but the distance.
Simple mechanical spiral
- A simple machine that belongs to the bevel category. For example, screw jacks can lift heavy objects. It is a labor-saving machine. The jack is lifted by a male spiral rod in a female spiral tube to lift the weight. According to the principle of work, the screw is rotated once under the action of power F, and the work F does to the screw is F2L. The spiral rotates once, and the weight is lifted by a pitch (that is, the vertical distance between the two threads). The work done by the spiral to the weight is Gh. According to the principle of work
- With a small force, you can lift a heavy object. The spiral is inefficient due to friction. Even so, the force ratio G / F is still high, and the distance ratio is determined by 2L / h. The use of spiral can be divided into three types: fastening, force transmission and transmission.
Simple mechanical gears and gear sets
- The two gears that mesh with each other do not save effort when they are in equilibrium, because the essence of the gear is two equal arm levers, so the gears that mesh with each other do not save effort, only the number of turns.
Simple mechanical chopping
- Also known as "split", commonly known as "wedge". It is one of the simple machines and its cross section is a triangle (isosceles triangle or right triangle). The bottom of the triangle is called the split back, and the other two sides are called the split edge. When force F is applied to the split, the force acting on the object being split is split into two parts by the split blade. P is the resistance added to the split. If the friction between the split and the object is ignored, the force decomposition method is used. Knowing that P is perpendicular to the slope of the cleavage, the action of P can be divided into two component forces: one is perpendicular to the direction of cleavage's movement, and its magnitude is equal to P · cos, which has no effect on the movement; the other is opposite to the direction of cleavage's movement. Yes, its size is equal to P · sin, which hinders movement. Therefore, the split can advance only when F = 2P · sin, so the ratio of the size of P to F is equal to the ratio of the length of the split surface and the thickness of the split back. Therefore, the thinner the split back and the longer the split surface, the more effort is saved. There are many uses for chopping, which can be used as cutting tools, such as knives, axes, planers, chisels, shovels, etc .; it can be used to fasten objects, such as shoe lasts, axe handles, and wedges to tighten them; it can also be used to lift Such as changing columns and beams during house repairs.
Simple mechanical work
- It is a physical quantity describing the change of state of an object, a measure of energy change. The concept of work comes from the word "work" in daily life. In physics, it has a special meaning. When an object is under the action of a constant force F and the displacement of the point of application of the force is S, this work is equal to the product of the force and the distance. For junior high school students, as long as it is clear that under the action of force, an object passes a distance in the direction of the force, then the force does work on the object, which means that the object is in the direction of the force under the action of constant force. In the case of one-way linear motion, the calculation of work can use the formula W = FS. When the object is under non-unidirectional linear motion under constant force, such as vertical throw motion, flat throw motion, oblique throw motion, etc., the force direction and motion direction of the object may not be consistent. The understanding of work should be The deepening is "the product of the force's work on the object, which is equal to the magnitude of the force, the displacement of the point of application of the force, and the cosine of the angle between the force and the displacement", ie W = FScos. In the formula, W represents the work done by the external force F on the object, S represents the distance the object moves, and represents the angle between F and S. Investigate some cases of force doing work on objects according to formulas:
- 1. When = 0 °, W = FS, the force does positive work on the object;
- 2. When 0 ° < <90 °, 1> cos> 0, the effective component force Fcos of the force F is consistent with the direction of motion of the object, and the force F performs positive work on the object;
- 3. When = 90 °, cos = 0, then W = 0, then force F does not do work on the object;
- 4. When 180 °> > 90 °, -1 <cos <0, then W <0, that is, W is negative. In this case, F does negative work on the object, which can also be said to be the object doing work to overcome the resistance F;
- 5. When = 180 °, then W = -FS. At this time, the force F does negative work to the object, or the object overcomes the resistance F to do work.
- It must be noted that, when studying the issue of "work", it should be distinguished whether there is work and who is doing it. Work is a physical quantity with only size and no direction. It is a scalar and not a vector. As for positive work and negative work, it is only a distinction between the external force doing work on the object or the object overcoming resistance to do work, or to indicate whether the force is in the same direction as the distance or not.
- Work is the cumulative effect of force on space. The force does work on the object, causing the object to change its position or movement state, so the mechanical energy changes. Work is a physical quantity that reflects how much an object's mechanical energy changes during this process. The narrow concept of work in mechanics refers only to the measurement of mechanical energy conversion; the broad concept of work in physics refers to the measurement of all energy conversions except heat transfer. So work can also be defined as a measure of energy conversion. The change in the total energy of a system is often measured by how much work the system does externally. Energy can be in various forms such as mechanical energy, electrical energy, thermal energy, chemical energy, etc., and multiple forms of energy can be converted simultaneously. The units of work are the same as the units of energy. In the international unit system, they are both joules.
- The calculation of variable force work is to divide the trajectory of motion into many infinitely small segments. In each segment, the force can be regarded as constant force. The work done in each segment is calculated according to the definition of constant force work. Finally, Adding the work of each segment is the work of variable force, that is, A = Fi · Si. If the force and displacement are continuous, it can be calculated by the integration method.
Principle of simple mechanical work
- Also known as "Principle of Mechanical Work". That is, the work that power does to the machine is equal to the work that the machine does to overcome the resistance. In other words, no machine can save energy. Power work W is also called input work or total work. Resistance work W resistance, including W useful (also known as output work) to overcome useful resistance and W useless (also known as lost work) to overcome useless resistance, that is, W action = W resistance = W useful + W useless. It can also be written as W input = W output + W loss. The principle of work is the basic principle of machinery. To save effort, you need to move more distance, and to move less, you need to use more force. You can't save effort by using any machinery. In the process of mechanical work, the effective work is equal to the total work, and the efficiency is 100% only in the ideal case where there is no useless resistance and the machine itself moves at a uniform speed. In fact, there must be useless resistance, and the efficiency must be less than 100%, which means that the use of any machinery is always laborious under actual conditions. It should be clear that only in ideal situations useful work equals total work.
Simple mechanical positive work
- When the angle between the direction of the applied force and the direction of displacement of the applied point of the force is less than 90 ° and greater than or equal to 0 ° (that is, is an acute angle), the positive force A is used to do positive work. When the angle between the force F and the displacement S is = 0 °, W = FScos0 ° = FS, F performs the maximum positive work; 0 ° < <
Simple mechanical negative work
- When the angle between the direction of the applied force and the direction of displacement of the applied point of the force is greater than 90 ° and less than or equal to 180 °, at this time cos <0, and the work is negative according to the formula. Negative work of force on the object-A means that the object acting on the force overcomes resistance to make positive work A. These two statements describe the same physical process. For example, the negative work of air in the air compressor on the piston can also be said to be the positive work of the piston against the pressure of the air. For another example, the car brakes suddenly, the wheels stop rotating, and the tire slides on the ground. At this time, the friction force does negative work to the car, and in turn, it can be said that the car overcomes the friction force to do positive work.
Simple mechanical power
- The ratio of work to the time it takes to complete them is called "power." The power was initially defined as "work done in a unit time", which refers to the situation in which the work is performed at the same speed, which is easy for junior high school students to master. The defined power of "the ratio of work to the time it takes to complete these work", for cases where the speed of work is constant, represents both average power and instant power. For the case of uneven work speed, if the time is longer, it is the average power; the time tends to zero, this
- The rate can only represent the average power of the machine over a period of time t. The power calculated by the formula P = Fv has different meanings. If the speed v represents the average speed, then P represents the average power, and if v represents the instantaneous speed, then P represents the instantaneous power of the machine at a certain instant.
- In the formula, force is a vector, velocity is a vector, and power is a scalar.
- Methods, one is "scalar product"; the other is "vector product". The "scalar product" of two vectors is a scalar, and its size () is the product of the magnitude of the two vectors and the cosine of the angle between the two vectors, which is expressed by the formula:
- In the formula P = Fv, in fact, P should be the scalar product of the vector and the vector, that is,
- So the obtained power P should be a scalar.
- Regarding the formula P = Fv, the inverse relationship between F and v in the formula should be clear, and cannot be separated from the specific conditions to prevent false results. Because the traction of the machine is limited by the speed and by the structure and operating conditions of the machine, any machine has been specified for its normal power and maximum force when designed and manufactured. Beyond the maximum force range, the relationship between traction and speed is not applicable. On the other hand, the traction of the machine cannot be approached to zero, and the speed of the machine can be increased without limit. Because any machine is subject to resistance at work, resistance is also related to the speed at which the machine runs. Even under no load conditions, the frictional resistance between parts still exists. To keep the machine running, the traction of the engine must not be less than the resistance it receives. Therefore its speed cannot be infinitely increased. Therefore, while any machine has a certain maximum output power, it also has a certain maximum speed and maximum force.
- A common unit of power is Watts (joules per second), referred to as watts, and the unit symbol is W. Watt is a small unit. Technically, kilowatts are commonly used as a unit of power. In the past, there were ergs / second, Newton meters / second, and kilogram-force meters / second.
- The average power in time t. When an object is subjected to constant force, it can also be expressed as P = F. The formula represents the average speed over a period of time. The average power varies with the time taken, so when talking about average power, be sure to indicate which period of time the average power was. See Power Bar.
Simple mechanical instant power
- That is "instantaneous power", referred to as power. Describe the mechanics at a certain moment
- Product of the instantaneous speed of an object's movement. When making the average speed, P of course represents the average power. If it is the instant speed, then P represents the instantaneous power of the machine at a certain instant. When used as a uniform speed, the instantaneous power and the average power are the same
- Lever concept: When the distance between the power point and the fulcrum is less than the distance between the resistance point and the fulcrum, it saves effort.
- When the distance between the power point and the fulcrum is greater than the distance between the resistance point and the fulcrum, it is laborious.
- When the distance between the power point and the fulcrum is equal to the distance between the resistance point and the fulcrum, it is not labor-saving and effortless.
Simple mechanical classification
Simple mechanical first classification
- The first type of leverage: Power F and useful resistance W are on both sides of the fulcrum. This type of leverage
- No effort or effort. For example, the scissors used to cut metal plates have short blade edges, and their mechanical benefits are much greater than one. This is because the metal plate is very hard, the knife edge is short, and the handle is long, that is, the power arm is larger than the resistance arm, which can use less force. There are also levers such as pliers. Scissors used for household clothes cutting and cutting are basically the same length as the blade, that is, the power arm is equal to the resistance arm, which belongs to a type that is not labor-saving or labor-intensive. Because the thickness of the cloth is thin and does not require too much force, the cloth should be straight, so the knife edge should be longer. For this reason, the force is not strong, and the cloth is straight. Also of this type are physical balances. Another example is the scissors for hair cutting. The blade is very long, that is, the power arm is smaller than the resistance arm, and its mechanical benefit is less than 1. This is because hair cutting does not require much force, the knife edge is longer, and it can be cut faster and more uniformly.
- The second type of leverage: the fulcrum and power point are on both sides of the useful resistance point. The power arm of this type of lever is larger than the resistance arm, and its mechanical benefit is always greater than 1, so it is always labor-saving. For example, hoeing with trowels, unicycles, etc. are all such levers.
- The third type of lever: the fulcrum and the useful resistance point are on both sides of the power point. The power arm of this type of lever is smaller than the resistance arm, and its mechanical benefit is always less than 1, so it is always laborious. For example, pedals for sewing machines, and bamboo clips for food are all such levers.
Simple mechanical second classification
- The first type of lever is a labor-saving lever, that is, the power arm is larger than the resistance arm. For example, claw hammers, woodworking pliers, unicycles, soda boards, trowels, and so on.
- The second type of lever is a laborious lever, that is, the power arm is smaller than the resistance arm. Such as tweezers, fishing rods, hair clippers.
- The third type of lever: a lever that is effortless and effortless, that is, the power arm is equal to the resistance arm. Its mechanical benefit is equal to one. Such as balance, fixed pulley and so on.