"Lever" Simple Machine Function PPT Courseware 4

Description

"Lever" Simple Machine Function PPT Courseware 4

teaching objectives:

1. Understand leverage and several concepts related to leverage

2. Know the conditions and applications of leverage balance

3. Learn to analyze experimental phenomena and summarize general methods of experimental conclusions.

1. What is leverage?

Definition: A hard rod that can rotate around a fixed point under the action of force is a lever.

Note: A hard rod does not deform or basically does not deform under the action of force. It can also be curved, that is, the hard rod can be in various shapes.

Lever: A stiff rod capable of rotating about a fixed point under the action of force

Fulcrum (o): The point around which the lever rotates

Power (F1): the force that causes the lever to rotate

Resistance (F2): the force that hinders the rotation of the lever

Power arm (L1): the vertical distance from the fulcrum to the power line of action

Resistance arm (L2): the vertical distance from the fulcrum to the resistance line

(Line of action of force: point of action of overforce, straight line along the direction of force)

The method of drawing the moment arm is: first, find a point, second, draw a line, and third, make a vertical segment.

(1) First determine the fulcrum O of the lever and the direction of drawing power and resistance.

(2) Draw the line of action of the force along the direction of the force's action point.

(Note: When drawing, use dotted lines to extend the line of action of the force.)

(3) Use a solid or dotted line as a vertical line from the fulcrum O to the line of action of the force, and draw a vertical symbol. Then the distance from the fulcrum to the vertical foot is the moment arm.

(4) Finally, use braces or arrows to outline the moment arm, and write the letters L1 or L2 next to it. (Two ways to express the moment arm: braces and arrows)

guess:

1. Change the number of hooks on one side and observe what will happen?

2. Change the hanging position of the hook code on one side and observe what will happen?

3. Push the suspension line of the hook code on one side to change the direction of the force and observe what will happen?

4. What will happen if you change the suspension position (fulcrum) of the lever?

Experimental notes:

1. Before the experiment, adjust the balance nuts at both ends of the lever to make the lever horizontally balanced.

2. After the hook is coded, the balance nut cannot be moved.

3. When reading, the lever is still required to be in a horizontal balance state so that the length of the force arm can be directly read.

Class summary

1. Lever definition: a hard rod that can rotate around a fixed point under the action of force

2. Composition:

Fulcrum (O): The fixed point around which the lever rotates

Power (F1): the force that causes the lever to rotate

Resistance (F2): the force that hinders the rotation of the lever

Power arm (l1): vertical distance from the fulcrum to the power line of action

Resistance arm (l2): the vertical distance from the fulcrum to the resistance line

3. Conditions for leverage balance: F1×l1=F2 ×l2→F1/F2=l2/l1

In-person test one

Find the force and resistance in each of the following diagrams and draw the lever arm.

The ratio of the power arm to the resistance arm of a lever is 3:2. To balance the lever, the ratio of power to resistance is _____.

In-person test 2

A lever AB is 1m long, and the fulcrum is 0.4m away from end B. As shown in Figure 3, an object G1 weighing 200N is hung on end A. If the lever is to be balanced, how many objects G2 must be hung on end B?

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

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Update Time: 2024-06-25

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

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