"Did you work?" 》Machine and Human PPT courseware

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"Did you work?" 》Machine and Human PPT courseware

mechanical work

In order to evaluate the effectiveness of machinery, the concept of work was proposed.

In physics, the product of force and the distance an object moves in the direction of the force is called mechanical work, or work for short.

Students carry their schoolbags and move forward at a constant speed on a level road.

(This scenario is similar to the animation below, please see Ling Gong)

(no work done)

Powerful F

There is a distance s

But the directions of F and s are vertical

(vertical reactive power)

Usually no work is done on the object in the following three situations:

①The object is acted upon by a force, but the object is stationary and has no distance traveled in the direction of the force. This force does no work on the object.

②The object is not acted upon by any force in the direction of motion. Due to the inertia passing through a certain distance, no force does work on the object.

③The object is acted upon by a force, and the object is also moving, but the direction of motion is always perpendicular to the direction of the force, that is, the distance the object moves in the direction of the force is zero, and this force does no work on the object.

Please fill in "Yes" or "No"

1 Shandong girl Tang Gonghong won a weightlifting gold medal in the Olympics. Her weightlifting process was divided into two processes: in the first stage, she grabbed the barbell and lifted it above her head; in the second stage, she held the barbell steadily in the air. It stopped steadily for 3 seconds.

Then she does ______ work in the first stage and ______ work in the second stage.

2. Xiao Ming kicks the ball away with his feet. While the ball is flying in the air, Xiao Ming's feet do ______ work on the ball.

3. Xiaogang carries a bucket of water and walks at a constant speed on a level road. His lifting force does ______ work on the bucket.

According to mechanics, work is equal to the product of force and the distance traveled by the object in the direction of the force.

Work = force x distance

W = F S

W——work

F——Force

S - distance in the direction of force

What is the unit of work?

The unit of F——N

The unit of S——m

The unit of W——?

The unit of W should be N·m

However, in order to commemorate the great scientist Joule, we call the unit of work "Joule" or the symbol for "Joule" is "J". Therefore: 1 J=1 N •m

What did you gain from studying this section?

mechanical work

In physics, the product of a force and the distance an object moves in the direction of the force is called mechanical work.

What counts as work?

Elements:

1. Force acting on an object

2. The distance traveled by an object in the direction of force

How to calculate work

Formula: W=Fs

Unit: 1J=1N*1m

Consolidation exercises

1. Object A moves on a smooth horizontal surface, and object B moves on a rough horizontal surface. Now use the same horizontal thrust to make A and B move the same distance in the same direction. The two work done are W A and W B respectively. Then WA______WB. (Fill in "〈", "=" or "〉")

2. The masses of two containers A and B are equal. Use a crane to lift container A 10m at a speed of 1m/s, and lift container B to the same height at a speed of 2m/s. Then we have W A ______ W B. (Fill in "〈", "=" or "〉")

Additional homework:

1. An object weighing 100N is pushed with a horizontal thrust of 60N to move in a straight line at a constant speed on the horizontal plane. It passes a distance of 80m in 4 seconds. During this time (1) what is the speed of the object? (2) How much work is done by the thrust?

2. A worker uses the pulley block shown on the right to lift a 1000N load. The force used is 600N, and the free end of the rope is pulled down 4m.

Ask: How much work did he do?

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For more information about the PPT courseware "Have Machines and People Done Work?", please click the "Have Machines and People Done Work ppt" ppt tag.

"Did you work?" 》Machine and Human PPT Courseware 2:

"Did you work?" 》Machine and Human PPT Courseware 2 Scenario Introduction In order to understand work in physics, let us analyze several examples. 1. The lifting force F of the forklift moves the goods a certain distance. We say that the lifting force of the forklift does work on the goods, or simply that the forklift does work on the goods..

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Update Time: 2024-09-17

This template belongs to Physics courseware Shanghai Science Edition 8th Grade Physics industry PPT template

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