跟读练习: Types of Levers - 通过视频学习英语口语

A lever is a simple machine that includes a bar that is free to move about a fixed point called a fulcrum.

Levers make work easier by reducing the effort required to move the load, but increasing the distance moved by the effort.

This can be achieved by moving the fulcrum closer to the load or applying the effort further from the fulcrum.

There are three types of levers.

First class levers, second class levers and third class levers.

Each type of lever makes work easier in different ways.

In a first class lever, the fulcrum is between the load and the place on the bar where the effort is applied.

This changes the direction of the effort.

Work is the easiest when the effort is applied to the bar as far from the fulcrum as possible.

The distance the effort moves is increased, but the force applied to the load is multiplied.

Moving the fulcrum closer to the load increases the distance the effort moves and increases the force applied to the load.

You use first class levers when you use pliers to pull a nail.

The piece of wood is the fulcrum.

The fulcrum is close to the load which increases the distance the effort moves and multiplies the force applied to the nail.

The back of a claw hammer, nail clippers and scissors are objects we use that function as first class levers.

In second class levers, the load is between the effort and the fulcrum.

The effort moves over a larger distance to raise the load a smaller distance, but with greater force.

The closer the load is to the fulcrum, the larger the distance the effort moves and the greater the force applied to the load.

Notice that in second-class levers, the effort applied is in the same direction as the force applied to the load.

Wheelbarrows, nutcrackers and bottle openers are objects we use that function as second-class levers.

In both first-class and second-class levers,

work is made easier by decreasing the effort required but applying the effort over a greater distance.

In a third class lever, the effort is between the fulcrum and the load.

Greater effort is required to move the load, but the speed at which the load moves is multiplied.

As in second class levers, the direction of the effort and the force applied to the load is in the same direction.

Fishing rods, baseball bats, and brooms are objects that function as third-class levers.

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什么是跟读法？

跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。

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跟读练习: Types of Levers - 通过视频学习英语口语

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