"The Principle of Work" Simple Machine Work PPT Courseware

Description

"The Principle of Work" Simple Machine Work PPT Courseware

learning target

(1) Understand the principle of work and know that using any machine does not save work;

(2) Learn to apply the principle of work to perform simple calculations;

(3) Understand the application of the principles of gong in life.

1. The principle of work

Compare the work done by the hand on the machine and the work done by the machine on the object in the above two experiments. What is the relationship between them?

Experiments have shown that the work done by people when using machinery will not be less than the work done without machinery, and no machinery saves work. This is the principle of gong.

Thinking: What is the reason for not saving effort?

There is no machine that saves both labor and distance.

Work = force x distance

2. Calculation of the principle of work

Assume that the inclined surface is smooth and frictionless.

According to the principle of work:

W is used = W is not used

The length of the incline is several times the height of the incline, and the thrust is a fraction of the weight of the object.

To raise objects to the same height, the longer the slope, the easier it is to lift it.

Solution: Weight of object G=mg=120 kg x 10 N/kg=1200 N

Since there is no friction on the inclined plane, according to the principle of work, we can get:

Fl=Gh

F=Gh/l

=1200 N x 1 m/3 m

=400 N

Summary of this lesson

What did you gain from studying this class?

1. The principle of work

The work people do when using machinery will not be less than the work done when not using machinery, that is, using any machinery will not save work.

Reasons why machinery does not save power

Reasons why we still use machines without saving energy

2. Calculation of the principle of work

Assume that there is no friction in the machine

Formula: FL=Gh

Practice in class

1. In mountainous areas, you can often see porters carrying heavy objects up the mountain and taking an S-shaped route on the slope. They do this for ( )

A． Make people do less work

B． Save people some effort

C. No reason, it's their habit

D. None of the above statements are correct

2. The principle of work tells us that using machinery can save labor, but not work. Why do people often take small paths when climbing mountains and don't like to take big roads? The roads on the board are all sloped, wouldn't it save effort?

3. Use the two devices A and B shown in the figure to raise the same object by 1 meter. If friction and the weight of the pulley are not included, then the work done by the pulling force F is ( )

A． Lots of armor

B． Yiduo

C. As much

D. Can't compare

4. As shown in the figure below. Tie one end of the rope to the top of the smooth incline, loop the rope around the log, and pull the other end of the rope with your hand to pull the log up the incline. It is known that the mass of the log is 20 kg, the length of the inclined plane is 4 meters, and the height is 1 meter. Disregarding friction, find the pulling force of the hand and the work done by the pulling force.

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For more information about the "Principles of Simple Mechanical Work" PPT courseware, please click on the "Principles of Simple Mechanical Work ppt PPT" tag.

"The Principle of Work" Simple Machine Work PPT Courseware 2:

"The Principle of Work" Simple Machine Work PPT Courseware 2 Class Presentation 1 1. What are the labor-saving, distance-saving, and direction-changing machines that we have learned? 2. Is there any machinery that saves both labor and distance? Class Demonstration 2: Cooperate within the group to solve the following problems and demonstrate:..

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Update Time: 2024-10-08

This template belongs to Physics courseware Lu Jiao Edition Eighth Grade Physics Volume 2 industry PPT template

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