"Power" Work and Mechanical Energy PPT Courseware 4

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"Power" Work and Mechanical Energy PPT Courseware 4

How to compare the speed of work done

Question 1: Send all the same pile of bricks to the roof of the building at the construction site. The method is as follows:

1. Use the pulley to transport the bricks upstairs. 2. Use the crane to transport the bricks upstairs.

ask

1) Do these two methods perform the same work?

2) Does the work take the same time?

3) Who does the work faster? We can see what methods we can use to compare the speed of work

Question 2: On a construction site, a pulley or a crane is used to transport bricks to the roof of the building at the same time. It takes 15 minutes to transport bricks. Which method does more work? Who does the work faster? So what other methods can we use to compare the speed of work done by objects?

Question 3: Xiao Ming uses a shovel to dig soil. He does 600J of work in 10 minutes. His father does 300J of work in 1 minute. Who does more work? Who does the work faster? Why?

The more work done per unit time, the faster the work is done.

The speed of work can be compared with the work done per unit time.

The work done per unit time is called power.

The greater the power, the more work is done per unit time, that is, the faster the work is done.

Symbol:P

The power of a person riding a bicycle is about 60~70W;

The power used by people when doing manual labor is about 30~80 W;

A high jumper who jumps over 2 meters can perform work up to 1500 W in a very short time;

A weightlifter's instantaneous power can also exceed 1500 W;

The power of a horse working for a long time is about 300~450W;

The power of a blue whale when swimming can reach 350 KW.

I can do it

1. Power means _____ of work done. The greater the power, the more ____ of work done. The size of the power is determined by ____ and ___.

2. Trial judgment (P=W/t)

The more work A does, the greater the power ( )

B has small power, which means less work is done. ( )

The shorter the work time of C, the greater the power ( )

If D does work quickly, the power is high ( )

Thoughts and Practice

1. Regarding power, which of the following statements is correct ( )

A The less time it takes to do work, the greater the power

B The greater the power, the more work is done

C In the same time, the more work is done, the greater the power

D The more time it takes to do work, the greater the power

2. Two machines, the power of A is 750 watts and the power of B is 2250 watts. The ratio of the work done by A and B in the same time is ( ); if the same work is completed, the ratio of the time taken by A and B is ( ). )

Keywords: work and mechanical energy teaching courseware, power teaching courseware, New People's Education Edition eighth grade physics PPT courseware volume 2, eighth grade physics slide courseware download, work and mechanical energy PPT courseware download, power PPT courseware download, .ppt format

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Update Time: 2024-10-20

This template belongs to Physics courseware People's Education Edition Physics for Grade 8, Volume 2 industry PPT template

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