"What is called work" Mechanical work and mechanical energy PPT courseware 2

Description

"What is called work" Mechanical work and mechanical energy PPT courseware 2

1. Find commonalities in activities

2. Work in mechanics

1. Work: If a force acts on an object and the object moves a distance in the direction of the force, the force has done work on the object.

The lifting force F of the forklift moves the goods a distance S. We say that the lifting force of the forklift has done work on the goods, or simply that the forklift has done work on the goods.

Do you know what criteria you use to determine whether work is done?

necessary factors

F (force acting on an object)

s (distance the object moves in the direction of the force)

Cranes and helicopters lifting heavy objects are examples of work done. Do you know why force does work?

reason

A force acts on an object.

The object moves a certain distance in the direction of the force.

3. Determine whether the object is doing work

The situation of not doing any work

1. There is a force, but the distance traveled in the direction of the force is zero.

2. There is distance, but there is no force acting in the same direction as the distance

3. There is force and distance, but the directions of force and distance are perpendicular to each other.

4. Calculation of work

1. It is stated in mechanics that work is equal to the product of force and the distance traveled by the object in the direction of the force.

That is: work = force × distance

If F is used to represent force, S represents the distance traveled by the object in the direction of the force, and W represents the work done by the force.

Then: W＝Ｆ×Ｓ

Expressed in words: 1 Joule = 1 Newton × 1 meter

Meaning: If a force of 1 N is used to move an object 1 meter in the direction of the force, the work done by the force on the object is 1 Joule.

practice

1. When a weightlifter holds the barbell motionless, the lift does work.

2. A person lifts a heavy object and moves it at a constant speed in the horizontal direction for a certain distance. The lifting force does work on the heavy object.

3. When an apple falls from the tree, gravity does work on the apple.

4． The ball moves a certain distance on a smooth surface, and the support force of the table does work on the ball.

5. The car weighs 200N and a person uses a horizontal force of 30N to push the car forward 50m along a level road at a constant speed. Which of the following is correct ( )

A． The work done by gravity is 10000J

B． The work done by a person on the car is 10000J

C. The work done by a person on the car is 1500J

D. The resistance on the car is 230N

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"What is called work" Mechanical work and mechanical energy PPT courseware 3:

"What is Gong?" Mechanical Work and Mechanical Energy PPT Courseware 3 What do you think is Gong? Tell me: What is the meaning of Gong in life? How many idioms containing the word "gong" can you name? The meaning of gong: (1) It means to contribute. Such as: great achievements, outstanding achievements, etc. (2..

"What is called work" mechanical work and mechanical energy PPT courseware:

"What is called work" Mechanical work and mechanical energy PPT courseware learning objectives 1. Be able to name the two necessary factors for doing work. 2. Be able to judge whether force is doing work on an object. (Key points) 3. Be able to use the calculation formula of work to perform simple calculations Calculation. (Difficulty) We often see in life...

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Update Time: 2024-09-08

This template belongs to Physics courseware Guangdong and Shanghai Edition Ninth Grade Physics Volume 1 industry PPT template

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