"Free Fall Motion" Research PPT Courseware on Uniform Speed ​​Linear Motion

Description

"Free Fall Motion" Research PPT Courseware on Uniform Speed ​​Linear Motion

Part One: Learning Objectives

1. Know the conditions, properties and characteristics of free fall motion. (emphasis)

2. Master the laws of free fall motion, be able to measure the acceleration of free fall motion through experiments, and know that the magnitude of gravity acceleration is different in different places on the earth.

3. Understand the process of Galileo's study of free fall motion and understand his research methods. (difficulty)

Free fall motion PPT, part 2: exploration of new knowledge

1. Free fall motion

1. Aristotle's point of view: The speed at which objects fall is determined by their ______.

2. Galileo's research

(1) Reductio ad absurdum: Galileo started from the assertion of _______________ and denied his assertion through logical reasoning.

(2) Conjecture: Free fall motion is the simplest variable-speed motion, and its speed should be ____________.

3. free fall motion

(1) Definition: The movement of an object starting to fall from ______ only under the action of ______.

(2) Nature of motion: ________ linear motion with initial velocity of zero.

2. Free fall acceleration

1. Definition: At the same place, the acceleration of all objects falling freely is ______. This acceleration is called the acceleration of free fall, also called _______________, usually represented by g.

2. Direction: Always____________.

3. Size: The size of g is different in different places on the earth. In general calculations, g is taken as ____________. In approximate calculations, g is taken as ____________.

3. Laws of free fall motion

1. Speed ​​formula: v=______．

2. Displacement formula: h=______.

3. Velocity displacement formula: v2=______.

self-test

Thinking Analysis

(1) The falling motion with an initial velocity of zero is a free falling motion. ()

(2) The falling motion only under the action of gravity is free falling motion. ()

(3) The direction of gravity acceleration must point to the center of the earth. ()

(4) The heavier the object, the greater the acceleration of gravity and the faster it falls. ()

(5) Aristotle’s method of studying the laws of nature is experimental. ()

(6) Galileo's method of studying the laws of nature is a method that combines conjectures and hypotheses, mathematical reasoning and scientific experiments. ()

basic understanding

(1) (2019·Pinggu Final) The BBC science program "HumanUniverse" once conducted such an experiment in the world's largest vacuum laboratory: in a vacuum environment, an iron ball and a feather were released simultaneously from the same height. According to what has been learned Knowledge judgment, the phenomenon we will see is ()

A. The iron ball falls fast

B． Feathers fall fast

C. The iron ball falls as fast as the feather

D． Neither the iron ball nor the feather will fall

Tip: Choose C. If the room is filled with air, due to the influence of air resistance, neither will move freely. At the same time, because the feathers are greatly affected by air resistance, the iron ball and the iron ball will fall quickly; in a vacuum environment, Since both are subject to free fall motion only under the influence of gravity, the iron ball and the feather fall as fast, so C is correct and A, B, and D are incorrect.

(2) Pictured is the famous Leaning Tower of Pisa. Legend has it that Galileo once conducted experiments on the Leaning Tower of Pisa. Galileo let a heavy iron ball and a light iron ball fall at the same time, and found that the two balls landed almost at the same time, with a difference of only "two finger widths". Why is this?

Tip: "Landing to the ground almost at the same time" proves: the heavy iron ball and the light iron ball fall to almost the same height within the same time. The "two finger width" difference is caused by air resistance.

Free fall motion PPT, the third part: teacher-student interaction

Understanding and application of free fall motion

Problem guide

As shown in the figure, a small metal ball is released from rest at a height h above the ground. The small ball falls for a while and lands. Let’s discuss the above phenomena:

(1) What are the motion properties of the ball?

(2) How to determine the landing time and speed of the ball?

Key points: (1) The free fall motion of the ball is a uniformly accelerated linear motion with an initial velocity of zero: v0=0, a=g.

(2) The landing time and speed can be determined by the kinematic formulas h=12gt2 and v2=2gh.

【Core Deepening】

1. The essence of free fall motion

Free fall motion is a uniformly accelerated linear motion with initial velocity v0 = 0 and acceleration a = g. It is only a special case of uniformly variable linear motion.

Note: Objects can also undergo free fall motion on other planets, but the gravity experienced by the same object on different planets is generally different, so the acceleration when falling is generally different.

2. Free fall acceleration - acceleration due to gravity

Cause: Objects on the earth are attracted by the earth

size

It has nothing to do with the mass of the object, but to do with the position on the earth and the height from the ground. In general calculations, g=9.8 m/s2 or g=10 m/s2 can be taken

relationship with latitude

On the Earth's surface, the acceleration due to gravity increases with increasing latitude. The acceleration due to gravity is minimum at the equator and maximum at the poles, but the difference is very small.

Key competency 1: Understanding of free fall motion

(Multiple choices) (2019•Jinan High School January Examination) Regarding free fall motion, which of the following statements is correct ()

A. A piece of paper falls freely on the surface of the earth, which can be seen as a free fall motion.

B． A steel ball falls freely on the surface of the earth, which can be regarded as free fall motion.

C. At the same place on the earth, all objects in free fall have the same acceleration when they fall to the same height.

D． The acceleration due to gravity is different between light and heavy objects

Key Ability 2 Application of the Law of Free Fall Motion

A small ball falls freely from the air 80 m above the ground. (Ignoring air resistance, take g=10 m/s2) Find:

(1) How long does it take for the ball to fall to the ground;

(2) The speed of the ball when it falls to the ground;

(3) The ball’s displacement in the last 1 s since it started falling.

Key Capability 3: Equivalent conversion method to solve the problem of free fall motion

(2019•Changle Final) Qingqing is a girl who is good at thinking. After learning the laws of free fall motion, she became interested in the raindrops falling from the eaves of her house. The height of this eaves from the ground is 3.2 m. She sat in front of the window and noticed that a drop of water dripped from the eaves at equal intervals. When the fifth drop was about to drip, the first drop just fell to the ground, and the third drop and the second drop just fell to the ground. The drops are located on the upper and lower edges of the window, as shown in the figure. Taking g as 10 m/s2, find: What is the height difference between the upper and lower edges of the window?

Summary of rules

(1) Free fall motion is a uniformly accelerated linear motion with an initial velocity of 0, and its acceleration is g. The size of g has nothing to do with the magnitude of gravity. All the laws of uniformly variable linear motion are applicable to free fall motion, but it must be Note that when the question specifies (or implies) that air resistance cannot be ignored, the motion of an object falling from rest is no longer a free fall motion.

(2) Three points of attention in free fall motion

The laws are the same. When any object is in free fall, the motion laws are the same.

Movement speed It is known from v=gt that the longer the movement time, the greater the speed, and the movement speed is proportional to time; it is known from v=2gh that the greater the falling height, the greater the speed, and the falling height determines the speed.

Falling time: From h=12gt2, we get t=2hg, that is, the time of free fall is determined by the height of the fall.

[Exercise to achieve standards]

1. (2019•Anhui Qingyang High School First Phase) Xiao Ming shakes the apple tree, and an apple and a leaf fall from the same height at the same time. It is found that the apple falls to the ground first, then the following statement is correct ()

A. The motions of apples and leaves are both free fall motions

B． The motion of apples and leaves can be seen as free fall motion

C. The motion of an apple can be approximately regarded as a free fall motion, but the motion of a leaf cannot be regarded as a free fall motion.

D． If there was no air on the earth, apples and leaves would not fall to the ground at the same time

2. (Multiple choice) Regarding free fall motion, which of the following statements is correct ()

A. It is a uniformly accelerated linear motion with v0=0, a=g, and direction vertically downward.

B． The ratio of the displacements passed in the first three consecutive 1 s is 1:3:5

C. The ratio of the speeds at the end of the first three consecutive 1 s is 1:2:3

D． The ratio of the time from starting to falling 4.9 m, 9.8 m, and 14.7 m is 1:2:3

3. (2019•Foshan Final) When Xiaoxiao was watching a diving competition, a question came to his mind: How deep should the water in the pool be at least to ensure the safety of the athletes? He made the following assumption: During the competition, athletes jump upward from a platform 10 meters above the water, and when they reach the highest point, their center of gravity is about 1.25 m away from the platform. Then it falls freely; ignore the air resistance and regard the athlete as a particle, which decelerates in a straight line motion in the water; I found on the Internet that the average acceleration is 25 m/s2, and g is 10 m/s2. Please help Xiaoxiao calculate:

(1) The athlete’s speed when falling to the water;

(2) In order to prevent athletes from colliding with the bottom of the pool, the minimum water depth of the pool.

Free Fall Movement PPT, Part 4: Focus on Core Competencies

Comprehensive application of free falling motion and vertical upward throwing motion

General motion has multi-object and multi-process characteristics. Typical questions are as follows:

(1) The problem of encounter between free falling body and vertical projectile body

When two objects make free fall motions from different positions one after another, or two objects make free fall motion and vertical upward motion respectively, the condition for the two objects to meet in the air is that the two objects are in the same position at the same time.

The encounter problem of the above two objects can be solved with the ground as the reference system, according to the law of free fall motion and the displacement relationship and the time relationship. It can also be solved using a certain object as the reference system, based on the relative uniform motion of the two objects and combining the relative displacement and time. Solving time relationships.

For the problem of two objects undergoing free fall motion and vertical upward motion respectively meeting in the air, the rising process can also be solved by combining the critical conditions of the vertical upward motion, such as "just reaching the highest point" and "just returning to the ground". Or the conditions for encountering during the descent, etc.

(2) Multi-body problems in vertical upward throwing motion and free falling motion

Multi-body problems in vertical upward motion and free fall motion generally have the following characteristics:

①Every object undergoes the same motion process;

②The time difference between each object starting to move is equal.

For such problems, such as dripping water from faucets, continuous ball throwing by acrobats, fixed-point airdrops from helicopters, etc., multi-body problems can be converted into single-body problems and then solved.

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For more information about the PPT courseware "Research on Uniform Speed ​​Linear Motion and Free Fall Motion", please click on the "Research on Uniform Speed ​​Linear Motion Free Fall Motion" ppt tag.

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Update Time: 2024-10-19

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