﻿ 液压传动——能量的基础知识-行业资讯-杭州耐准精密机械有限公司

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• 液压传动——能量的基础知识
• 本站编辑：杭州耐准精密机械有限公司发布日期：2019-10-27 17:14 浏览次数：

1、能量

2、力

1、巨石会何去何从呢？

2、火车会发什么变化？

F = 2500 kg x 9.81 m/s2

F = 24525 kg·m/s2

F = 24525 N

3、力矩

4、功

F = 15kg x 10 m/s2

F = 150 newtons

W = 150 newtons x 4 meters

5、功率

1, energy

Energy in real life is an invisible, intangible thing. It's just a term we use to describe the nature of an object, like color or warmth.

A fast moving object has greater kinetic energy;

A hot body has heat energy;

Fuels such as gasoline have chemical energy;

Moving electrons have electrical and electromagnetic energy.

When we say that an object has energy, we mainly focus on the following two points:

What will the energy cause to happen to the object itself?

How does energy change things around, that is, how does energy travel?

As we said before, energy is not something that you can actually see or touch, so it's hard to draw。 But if you look at figure 1, if you click on the GIF, you're applying some kinetic energy to it。

In conclusion, we know that energy can be transferred between different objects. See figures 2 and 3 for a good illustration of this.

When energy is transferred between objects, some energy must be lost in the process, mainly due to resistance such as friction.

We call them losses because they're not doing what we want them to do. That is, no useful work, do is useless.

In an automobile engine, for example, when chemical energy is converted from gasoline to kinetic energy, some of it is lost in the form of heat and noise.

The perfect engine is cold to the touch and completely silent. But no system in the world is so perfect. All the energy conversion systems we see in life have energy losses.

Because of the friction loss, we can conclude that the effective output energy is always less than the input energy. Figure 5 gives a good illustration of this conclusion.

But if you add in the energy lost, then the energy must be conserved, which is that the input energy is equal to the effective output energy plus the lost energy。 As shown in the following formula。

Energy input = energy output + energy loss

The law of conservation of energy says that energy can change from one form to another, but it is never created or destroyed. Whatever energy is produced at one point must dissipate somewhere.

The efficiency of the system is used to measure the proportion of the effective output energy in the total input energy. The more efficient the system, the more energy it USES for useful work, and the less energy it loses.

2,

A train, travelling at a very fast speed to the west.

Suddenly, the train hit a boulder. Oh, my god.

No casualties!

In fact, you only need to consider the following two questions:

1. Where will the boulder go?

The boulder would start moving west because the train was pushing it west.

The boulder moved, indicating that it had gained kinetic energy from the train.

The motion of the train slows down because it gives a kinetic energy of wind to the stone.

When the collision occurred, the train exerted a force on the boulder. That is, some of the energy on the train was transferred to the rock, so the rock moved.

What, then, is a force? It is an interaction between two objects that comes into contact and causes them to move relative to each other.

The most familiar force is gravity。 Your body is pulled towards the center of the earth by gravity。 If you jump into the air, gravity will pull you back to the ground。

A force causes a body to move either in a straight line or around a center. Figure 7 shows linear forces. Multiple forces can be applied to an object at the same time. In the forklift shown in figure 9, multiple forces are applied to the box as it moves up and down. How many forces are there? Think about it.

First, gravity always pulls a weight toward the ground, even when it's moving upwards.

Second, friction always ACTS to slow down the motion of the body. It takes kinetic energy from the body and converts it into heat and noise.

In addition, pressure is also a force. When hydraulic oils or compressed gases are compressed, they store a lot of energy in themselves. When pressure is released, energy stored in the oil or compressed air flows with the medium, lifting or lowering heavy objects. Even if a body is at rest, it does not mean that there is no force acting on it. Of course, if a body is at rest or moving at a constant speed, the force acting on that body is balanced.

If an object is in accelerated or decelerated motion, or the direction of motion is changed, the force on the object is unbalanced。

To solve for the force on an object, you need to know two things.

Mass -- you need to know what the object is made of。

Acceleration - the rate at which a body's speed changes as it accelerates or decelerates due to a force.

For example, we drop a weight of 2500kg from an aircraft, as shown in figure 11. Due to the force of gravity, the object will accelerate downward at an acceleration of 9.81m/s2. What is the force of gravity on the object? Let's look at the following calculation. Force = mass x acceleration, and the mathematical formula is F=ma

F = 2500 kg x 9.81 m/s2

F = 24525 kg · m/s2

F = 24525 N

Let's move on. Newton is a unit of force. Indicates how quickly this force can change the motion (acceleration, deceleration, change in direction) of a mass

If you want to change the speed of something that has a mass of 100 kilograms very quickly, you have to apply a lot of force to it.

If you want to change the speed of a 10kg mass very quickly, you need to apply a moderate force to it。

If you want to change the speed of a 100kg object slowly and gradually, you need to apply a moderate force to it.

If you want to change the speed of a 10 kilogram mass slowly and gradually, you need to apply a very small force to it.

3, moment

There are many ways to generate rotational forces。 The most common is shown in figure 12, where you use a vise to turn the bolt。

To calculate the torque in figure 12, we need to calculate the resultant force applied to the wrench and the length of the moment arm。

Figure 12

Torque is equal to force x moment arm

Torque = 15 newtons x 0.2 meters

Torque = 3 newton-meters (Nm)

So the torque applied to the vise is 3Nm. Remember, the units of torque are nanometers.

4, work

When a force is applied to a body, the body will change its original motion state, and at the same time, the body will gain or lose some energy。 To measure the magnitude of this energy, we introduce the concept of work。

If a force is applied to an object and does not change its motion, then no energy has been transferred, that is, no work has been done on the object. What does figure 13 tell you?

To calculate the amount of work, you must know two things:

The size of the force

The distance an object travels

Let's take an example, as shown in figure 14, of lifting a mass block of 15 kilograms up to a height of 4 meters。 For simplicity, let's take the acceleration of gravity as 10 meters per second

Figure 14

Force F is equal to mass m x acceleration a

F = 15kg x 10 m/s2

F = 150 newtons

Work W = force F x distance S

W = 150 newtons x 4 meters

W = 600 joules

The unit of work is joule J. 1 joule is the work done by a force of 1N applied to the mass, making it move 1 meter.

Although we use joules to measure the work done by a force on an object, joules can also indicate the amount of energy contained in an object. For example, the amount of energy in food, fuel, gasoline, etc., is expressed in joules. The two aren't contradictory, because work done by a force on a body is also the transfer of energy between bodies.

5, power

Power is the work done by a force on an object per unit of time. It's in J/s, which is also known as watt w.

Watt is named after James Watt, the inventor of the steam engine, and here is a head of a great man for you to admire.