"Pulley" Simple Machine Work PPT Courseware 2

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"Pulley" Simple Machine Work PPT Courseware 2

review

What is leverage?

What are the five elements of leverage?

How to draw a muscle arm? Step by step instructions?

What is the principle of leverage balancing?

Classification of leverage? What is the relationship between various lever arms?

learning target

1. Understand fixed pulleys and movable pulleys.

2. Know the functions of fixed pulley, movable pulley and pulley block.

3. Be able to use and assemble pulley blocks as required.

1. Get to know pulleys

1. What is a pulley?

A pulley is a wheel that has grooves around it and can rotate around an axis.

2. Classification of pulleys:

According to the movement state of the pulley, it can be divided into: fixed pulley and movable pulley

We can often see fixed pulleys and movable pulleys in daily life. Can students give some more examples? Please describe what type of pulleys they are.

Fixed and movable pulleys

fixed pulley

When in use, the shaft of the pulley is fixed

moving pulley

When in use, the shaft of the pulley moves with the object

1. Fixed pulley: a pulley with a fixed shaft.

1. Features: It cannot save effort, but it can change the direction of force.

2. Essence: equal-arm lever.

2. Moving pulley: The rotating shaft moves the pulley together with the heavy object.

1. Features: It can save half the effort, but cannot change the direction of the force.

2. Essence: The power arm is twice the lever of the resistance arm.

practise

1.The device shown in the picture is called ____________. When the object is raised at a constant speed, if F = 50 N, and the mass of the pulley is not included, the gravity exerted by the weight G is ______N.

If the object is to be raised 1 m, the free end of the rope should be pulled _____m.

2. As shown in the figure, a movable pulley with a weight of 10 N is used to lift a weight of 150 N. When friction is not considered, the minimum upward pulling force of lifting the weight at a constant speed is _____N.

3. The two pulleys shown in the figure both weigh 20 N, and the gravity of object G is 100 N. If the object is to rise at a constant speed, the pulling forces on the free end of the rope are FA=_____N, FB=______ _ox.

4. Someone wants to use four devices as shown in Figures A, B, C, and D to lift heavy objects. If the gravity of the pulleys in these devices can be ignored, in these devices, it is neither labor-saving nor labor-intensive. __________.

Consolidation exercises:

1: As shown in the figure (a) below, object B weighs 100N. When it rises at a constant speed under the action of force F, F should be equal to ____N. (excluding friction)

2: As shown in the figure (b) above, the weight of object A is 100N, and the tensile force endured by the hook hanging the heavy object is _____N. The force exerted by a person pulling the rope at a constant speed is ＿N (the dead weight of the moving pulley is not included)

3: Among the four pulley sets as shown in the figure, figure __________ can save half the effort, figure __________ is the most laborious, and figure __________ and figure __________ require the same amount of force.

1. Fixed pulley:

(1) Usage features: It can change the direction of force without saving effort or effort; without saving distance or distance.

(2) Essence: It is an equal-arm lever.

2. Moving pulley:

(1) Usage characteristics: It can save half the force, but does not change the direction of the force; it can move twice as far.

(2) Essence: The power arm is twice the lever of the resistance arm.

3. pulley block

(1) Advantages of use: It can save effort and change the direction of force; but it cannot save both effort and distance.

(2) Formula: F = G total / n = (G object + G moving pulley) / n (excluding pulley friction)

4. Axle:

1. The windlass on the well;

The power arm is larger than the resistance arm - a labor-saving lever.

2. Car steering wheel;

The power arm is larger than the resistance arm - a labor-saving lever.

3. Saving faucet:

The power arm is larger than the resistance arm - a labor-saving lever.

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

Five PPT charts of the relationships between pulley block designs:

This is a PPT chart of the relationship between five pulley block designs, in .PPTX format;..

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Update Time: 2024-09-12

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

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