"Circular Motion" PPT quality courseware

Description

"Circular Motion" PPT quality courseware

Part One: Core Competency Goals

physical concepts

Circular motion, uniform circular motion, linear velocity, angular velocity, period, frequency, rotational speed, coaxial transmission, belt transmission, chain transmission, and master the relationship between linear velocity and angular velocity.

scientific thinking

Combined with the common circular motion model in production, the meaning of each physical quantity can be further understood.

Scientific attitude and responsibility

Be good at observing and analyzing the characteristics of different sports in life.

Circular motion PPT, part 2 content: pre-class learning

Knowledge point 1 Linear speed

[Viewing pictures to help students]

(1) What do the movements of objects in the above daily life examples have in common?

(2) How to compare the movement speed of the second hand, minute hand and hour hand?

1.Linear speed

(1) Definition: As shown in the figure, the object moves from M to N along the arc. The ratio of arc length Δs to time Δt reflects the _______ of the object moving near point A. If Δt is very, very small, ________ can The ________ represents the movement of an object at point A, which is usually called the linear velocity.

(2) Expression: v=Δs/Δt.

(3) Direction: The direction of linear velocity is the tangent direction of the point when the object makes circular motion.

2. Uniform circular motion

If an object moves along a circle and the linear velocity is ________ everywhere, the motion is called uniform circular motion.

Knowledge point 2: Angular velocity

1. Definition: As shown in the figure, the object moves from A to B in Δt time. The ratio of the radius OA ____________ to the time Δt used during this period is called the angular velocity, represented by the symbol ω.

2. Expression: ω=Δθ/Δt.

3. Units: In the International System of Units, the unit of time is ______, the unit of angle is _________, the unit of angular velocity is ____________, and the symbol is _________.

Uniform circular motion is motion with constant angular velocity.

Three cycles of knowledge points

1. Period: For an object in uniform circular motion, the ______ used in the motion is called the period, represented by T. Period is also a commonly used physical quantity, and its unit is the same as the unit of time.

2. Rotation speed: Rotation speed is commonly used in technology to describe the speed of an object's circular motion. Rotation speed refers to the ratio of the number of turns of an object to the time it takes, commonly represented by the symbol n. The unit of rotation speed is revolutions per second (r/s), or revolutions per minute (r/min).

[Thinking and Judging]

(1) The greater the angle the object turns, the greater the angular velocity. ( )

(2) The faster the object rotates, the greater the angular velocity. ( )

(3) The hour hand has the largest angular velocity among the second hand, minute hand, and hour hand of the clock. ( )

Knowledge point 4: The relationship between linear velocity and angular velocity

1. The relationship between the two: In circular motion, the linear velocity is equal to the product of the angular velocity and the radius.

2. Relationship: v=ωr.

[Thinking and Judging]

(1) The greater the linear velocity, the greater the angular velocity must be. ( )

(2) The larger the rotation speed, the larger the period must be. ( )

(3) The greater the linear speed, the larger the period is not necessarily. ( )

Circular motion PPT, part three: core exploration

Core Point 1: Describing the physical quantities of circular motion and their relationships

Why do alarm clocks and watches have the above-mentioned speed dispute? Put forward your opinions and invite classmates to discuss.

Answer: "Alarm clock" and "watch" look at the speed of circular motion from different angles. The alarm clock refers to the linear speed of the second hand tip; the watch refers to the angular speed of the second hand rotation.

[Explore and summarize]

1. Comparison of various physical quantities

2. The relationship between linear velocity and angular velocity: v=ωr

(1) The relationship between the quantities in the formula

①When the radius r is constant, the linear velocity v is proportional to the angular velocity ω.

②When the angular velocity ω is constant, the linear velocity v is proportional to the radius r.

③When the linear velocity v is constant, the angular velocity ω is inversely proportional to the radius r.

(2) The relationship between various quantities is represented by images

[Examination Cases]

[Example 1] (Multiple choice) Two particles A and B are moving in a circular motion. The ratio of their angular velocities is 3:1 and the ratio of their linear velocities is 2:3. Then the following statement is correct: ( )

A. The ratio of their radii is 2:9 B. The ratio of their radii is 1:2

C. The ratio of their periods is 2:3 D. The ratio of their periods is 1:3

[For Training 1] (Multiple Choice) The train turned a curve at a speed of 60 m/s. A passenger found that the compass placed on the table rotated about 10° at a constant speed within 10 s. During this 10 s period, train()

A. The movement distance is 600 m B. The acceleration is zero

C. Angular velocity is about 1 rad/s D. Turning radius is about 3.4 km

Core Point 2: Several Common Transmission Devices

[Problem exploration]

The figure shows the model diagram of the two transmission devices.

(1) Figure A shows the belt transmission device. Try to analyze the relationship between the linear velocity and angular velocity of points A and B.

(2) Picture B shows a coaxial transmission device. Try to analyze the relationship between the angular velocity and linear velocity of points A and C.

Answer (1) In the case of belt transmission, in the same time, the arc lengths passed by two points A and B are equal, so the linear speeds of the two points are the same, and v=rω. When v is constant, the angular velocity is inversely proportional to the radius, The larger the radius, the smaller the angular velocity.

(2) In coaxial transmission, in the same time, the angles rotated by two points A and C are equal, so the angular speeds of these two points are the same, and because v=rω, when ω is constant, the linear speed is proportional to the radius , the larger the radius, the larger the linear speed.

[Examination Cases]

[Example 2] As shown in the figure, an ordinary wheelchair generally consists of a wheelchair frame, wheels, brake devices, etc. The wheels include large wheels and small wheels. A hand wheel is fixed on the large wheel, and the hand wheel is directly pushed by the patient. It is known that the ratio of the radii of the large wheel, the handwheel rim, and the small wheel is 9:8:1. Assume that the wheelchair moves in a straight line on the ground, and there is no slippage between the hand and the handwheel rim, or between the wheel and the ground. When the handwheel When the angular velocity of the pushing hand rim is ω, the angular velocity of the small wheel is ()

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Update Time: 2024-09-27

This template belongs to Physics courseware People's Education Press High School Physics Compulsory Course II industry PPT template

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