"Power" Simple Machine Power PPT Courseware

Description

"Power" Simple Machine Power PPT Courseware

learning target

(1) Know how to compare the speed of work done by objects;

(2) Understand the concept, unit and meaning of power;

(3) Master the simple calculation of power.

1. Compare the speed of work done by objects

At the same time, when comparing how much work is done, the more work is done faster;

For the same amount of work, if the time required to do the work is compared, the shorter time will be faster.

The height is the same, the weight is the same, and the time is shorter to do the work faster;

The height is the same, the time is the same, the heavier object does the work faster.

How to compare the speed of work done by pulleys and levers

(1) The work done is equal to the time;

(2) It takes equal time to do more work.

How to compare work done quickly and slowly

Method 1: When W A = W B, the shorter the time, the faster the work will be done;

Method 2: When tA = tB, the one who does more work will do it faster.

If time and work are not the same, how to compare the speed of work?

2. Power

Thoughts and Summary

There are two ways to compare the speed of work done by an object: When W A = W B, the one with a shorter time will do the work faster; when t A = t B, the one with more work will do the work faster.

To compare how fast an object does work, two factors must be considered: how much work the object does; and how long it takes the object to do the work.

The speed of work is expressed by the ratio of the work done within a period of time to the time taken to do the work. This quantity is called power.

1. The ratio of work to time is called power P

Numerically equal to the work done per unit time.

2. Expression Power=work/time P=W/T

3. International unit: watt (watt, W)

Commonly used units:

1 kW = 103 W

1 MW = 106 W

Summary of this lesson

What did you gain from studying this class?

1. Compare the speed of work done by objects

(1) When the work done is equal, the work done is faster than the time, and the time is shorter;

(2) When the time is equal, the one who does more work will do more work faster than the one who does more work.

2. Power

The ratio of the work done by an object to the time it takes to do the work is called power. Power is a physical quantity that expresses how quickly an object does work.

(1) Formula: Power=work/time P=W/T

(2) Unit: Watt, referred to as Watt, symbol W

Practice in class

1. When using machinery to perform work, which of the following statements is correct ( )

A． A machine with high power must do more work than a machine with low power

B． A machine with high power must take less time to do work than a machine with low power.

C. A machine with low power will always work slower than a machine with high power.

D. None of the above statements are correct

2. Which of the following statements is correct and which is incorrect? Briefly explain the reasons.

(1) Machines with high power do more work

(2) Machines with high power do work quickly

3. The mass of the boulder is 6 t. The crane's hook lifts the boulder 1 m at a constant speed in 15 s. What is the power of the crane in lifting the boulder?

Solution: Because the crane moves at a constant speed, the pulling force on the big stone is equal to the gravity on the big stone, that is,

F = G = mg = 6×103 kg×10 N/kg = 6×103 N

The distance the stone moves in the direction of tension s =1m

The work done by the pulling force is: W = Fs = 6×103 N ×1 m = 6×104 J

The power of the crane to lift the cement board is P=W/t1=6×104J/15s=4×103W

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For more information about the "Simple Mechanical Work Power" PPT courseware, please click on the Simple Mechanical Work ppt Power ppt tab.

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Update Time: 2024-10-02

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

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