"Lever" Mechanical and Work PPT Courseware 3

Description

"Lever" Mechanical and Work PPT Courseware 3

draw a picture

Draw the moment arms of forces F1 and F2 in the figure below.

The light lever OA rotates around point O and is now stationary at the position shown in the figure under the action of forces F1 and F2. Draw force F2 on the diagram.

Classification and application of leverage

According to the leverage balance condition: F1×L1=F2×L2

If L1>L2, then F1

Features of labor-saving lever: saves effort but requires distance

According to the leverage balance condition: F1×L1=F2×L2

If L1F2; this lever is a laborious lever

Features of laborious lever: laborious but can save distance

According to the leverage balance condition: F1×L1=F2×L2

If L1=L2, then F1=F2; this lever is an equal-arm lever

Characteristics of the equal-arm lever: saving neither effort nor distance

Take a guess

As shown in the figure, the fulcrum of the light lever is 0, a weight G is hung at point B, and a force (not shown) is hung at end A to balance the lever in a horizontal position, then the lever ( )

A. It must be labor-saving B. It must be labor-intensive

C. No effort or effort

D. All of the above are possible

levers in the human body

If you bend over, your muscles exert a pulling force of nearly 1,200 Newtons. This is due to the fact that the lever formed between the lumbar muscles and the spine is also a laborious lever (pictured). Therefore, when bending down to lift a heavy object, the correct posture is to keep the heavy object as close to the body as possible. To avoid muscle strain.

When you raise your toes, the muscles behind your heels are working. Your toes are the fulcrum, and your weight falls between them. This is a labor-saving lever (pictured), and the pulling force of the muscles is smaller than the body weight. And the longer the legs, the easier it is to use.

When you bend your elbow to lift something heavy, your arm also acts as a lever (pictured). The elbow joint is the fulcrum, and there are muscles on the left and right sides of the fulcrum. This is a kind of laborious lever. To lift a weight, the muscles will expend more than 6 times of effort. Although it is laborious, it can gain speed.

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For more information about the "Lever Machinery and Power" PPT courseware, please click the "Lever PPT Machinery and Power PPT" tab.

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Update Time: 2024-09-09

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