Slide 2
Repetition
2 In the presence of atmosphere, the movement of falling bodies tends to be uniform.
Slide 3
3 Laws characterizing free fall if V0 = 0; V = gt if V0 = 0;
Slide 4
Repetition
4 1. In the tube from which the air has been pumped out, there is a pellet, a cork and a bird feather at the same height. Which body will reach the bottom of the tube later than others?
A) Drobinka. B) Cork. B) Bird feather. D) All three bodies will reach the bottom of the tube at the same time. 2. What is the speed of a free falling body after 3 seconds? V0=0m/s, g=10m/s².
A) 15 m/s B) 30 m/s C) 45 m/s D) 90 m/s 3. How far will a freely falling body travel in 4 seconds? V0=0m/s,g=10m/s².
A) 20m B) 40m C) 80m D) 160m 4. What distance will a freely falling body travel in the 6th second? V0 = 0 m/s, g = 10 m/s².
A) 55m B) 60m C) 180m D) 360m
Slide 5
5 11/17/2011 The movement of a body thrown vertically upward. Lesson objectives: 1. Make sure that the movement of a body thrown vertically upward is uniformly accelerated. 2. Obtain basic formulas for movement. 3. Give examples of such movement.
Slide 6
Formulas
6 The movement of a body thrown vertically upward. v = vо - gt y = ho+vot - gt2/2 The OY axis is directed vertically upward
Slide 7
Graphic representation of movement
7 Graph of speed versus time. Graphs of acceleration, path and coordinates versus time.
Slide 8
Movement of bodies thrown vertically upward at different speeds
8 Coordinate versus time V02>V01
10 The most warlike plant is the “mad cucumber.”
He goes “rabid” when he is fully mature.
The cucumber breaks away from its stem with a crash, and shoots 6-8 meters from the hole where the fruit's stem was just before.
It turns out that while the fruit is ripening, gases accumulate inside it. By the time they ripen, their pressure in its cavity reaches three atmospheres! Problem: At what speed must a stream of juice containing seeds erupt in order to reach the height indicated above? How does the energy of the seeds change? (The speed of the jet is 12.6 m/s, while the kinetic energy of the jet is converted into potential energy.) KONDRAKOVA N.V.
MUNICIPAL BUDGETARY EDUCATIONAL INSTITUTION SECONDARY SCHOOL No. 13 OF THE CITY OF STAVROPOL
Lesson topic:
"Free fall. Movement of a body thrown vertically upward"
Physics lesson in 9th grade (according to A.V. Peryshkin’s program basic level)
Goals:
Educational:
Identify and prove what determines the free fall of bodies and the motion of a body thrown vertically upward, using Galileo’s formula.
Educational:Mastering the skills and abilities to observe, collate, compare and analyze the data obtained; speak out on a given topic.
Educational: Formation of communication skills
and the ability to work in the “teacher-class” and “teacher-student” modes.Lesson type:
lesson of learning new material.Methods: problem-solving, visual, independent work, frontal questioning, problem solving.
Lesson accompaniment:Presentation “Free fall, movement of a body thrown vertically upward”, film fragment, materials of the EC TsOR, , experiments.
Lesson equipment:
Interactive whiteboard, multimedia projector
electronic didactic material for students, equipment: sheets of paper, book, aluminum and steel cylinders.
During the classes:Organizing time: Hello guys! From today we will consider the nature and laws of motion of bodies that are acted only by gravity.
Updating knowledge:There can be several types of movements under the influence of gravity: the movement of bodies thrown vertically up, vertically down, thrown horizontally. The importance of knowledge of these laws cannot be underestimated. They explain the movement of paratroopers, projectiles, and athletes on springboards
(slide 2)
Problematic question: Falling paper and book (first each item separately, and then the sheet lies on the book). Justify this phenomenon? (students' answer)
Right. Conclusion: If a light body falls slower than a heavy one, then it should “slow down” the fall of the heavy body and the combination of two bodies should fall slower than one heavy body.
Experience No. 2: Two sheets of paper fall, one of which is crumpled into a ball. Explain these actions? (students' answer)
Absolutely right. Conclusion: The time of falling does not depend on the mass of the body, since the mass is the same, but the shape is different ( slide 4)
Experience No. 3: Fall of weights weighing 50 g and 150 g. Why did the weights fall at the same time? (students' answer)
Conclusion: We are once again convinced that the time of fall does not depend on body weight! ( slide 5)
Now we will try to figure out how bodies fall, what the time of fall depends on, what will happen if we do not take into account air resistance.
Introduction to the topic: The theory of free fall was first put forward by the great ancient thinker Aristotle (student information).
Justify Aristotle's position on the issue of free fall (as a result of the discussion, students come to the conclusion that Aristotle's opinion is wrong) Let's look at the position of another scientist.
(We listen to a student's speech, accompanied by a presentation from the life of the scientist - physicist Galileo Galilei)
The famous “leaning” tower is the bell tower of the cathedral in the city of Pisa, part of an architectural ensemble of rare beauty. Thanks to its design flaw, it is known throughout the world. The tower reaches a height of 55 meters, and the inscription on it indicates that it was founded in 1174. In 1564, Galileo Galilei, the future famous scientist, was born in Pisa. Judging by his own stories, he used the Leaning Tower of Pisa for his experiments.
Galileo carried with one hand
Little ball of lead
And at the back the core is different
Three young men were dragging...
Kernels of different weights,
Galileo decided to reset.
Which one, professor?
Could it fall soon?
Justify the position of the scientist (students come to the conclusion that this scientist is right).
Yes, indeed bodies fall with the same acceleration in airless space, but where do these laws find application in real life:
Task No. 1 The teacher shows footage from everyone’s favorite cartoon “Three from Prostokvashino.”
Task No. 2 Let's listen to a presentation on how knowledge of the laws of free fall was used in the invention of the parachute (student presentation).
Task No. 3 I bring to your attention a short video - an animation showing the fall of bodies of different masses in a Newton tube. ( video)
Updating knowledge:What does what you saw have to do with the topic of our lesson? (students’ answer in groups: we are observing a free fall)
As you can see, a lot of interesting things are connected with the phenomenon of free fall or with the movement of a body under the influence of gravity. Let's summarize what free fall is, this will be the topic of our lesson. Open the textbook (page) and write down the definition in the notebook “Free fall is the movement of bodies only under the influence of the Earth’s gravity”
On the surface of the Earth, the fall of bodies is conventionally considered free, since when bodies fall in the air, the force of air resistance always arises, so heavier objects fall faster. Ideally free fall is possible only in a vacuum, where there is no air resistance, and regardless of mass, density and shape, all bodies have the same speeds and accelerations, which is what we observed in Newton’s tube.
During free fall, all bodies near the surface of the Earth, regardless of their mass, acquire the same acceleration, called the acceleration of gravity. Let's write down the value of this quantity in our notebook:
G=9.8 m/s 2 (10 m/s 2 )
To make sure that free fall does not contradict the laws of nature, let's imagine the movement of a body of mass m on a horizontal surface under the influence of a force F. Then, if the mass of the body doubles, the applied force will also double, provided that the nature of the motion is maintained ( slide 9 ). Now let’s mentally rotate the image by 90 0 . What will happen? That's right, falling vertically downward under the influence of gravity ( slide 10 ) Now let's try to derive formulas for the movement of a body downward and thrown vertically upward. First, let's figure out how the distance traveled depends on the time of movement. I bring to your attention an interactive model of the movement of bodies down/up(slide 11)
We conclude: (children's answer based on the graphs) the distance traveled is directly proportional to the square of time, therefore, free fall is uniformly accelerated motion.
Guys, write these formulas in your notebooks ( slide 12).
υ=gt (body speed in free fall)
S= t 2 (free fall movement, height)
You have cards on the edge of the table. They draw an analogy between uniformly accelerated motion and the up/down motion of a body. Let's analyze these formulas in groups
Reflection : I think you and I have learned quite a lot of new things. I propose to consolidate the acquired knowledge in the process of solving problems that are encountered in the State Academy of Physics. Three students from each group solve problems at the board. The class will solve problems using cards in groups. (Appendix) We analyze the solution of problems on the board (evaluation criteria on the board).
Summarizing: Let's remember the students' performance.
What historical facts did you become familiar with today?
What knowledge did you gain? What did you learn? What difficulties did you encounter when solving problems? What formulas did we derive in class today?
I want to acknowledge the active work(we give grades, comment on the work in groups and write down homework (slide 16).
Homework: Textbook § 13-14 teach, pp. 52 – 58, Exercise 13 No. 1, p. 56
Exercise 14, p.60
Thanks for the lesson, goodbye!
Literature, sources of information:
1. Tutorial: A.V. Peryshkin, E.M. GutnikPhysics 9th grade. M.: Bustard, 2013.
2. . Volkov V. A., Polyansky S. E. Lesson developments in physics, grade 9,
M. Vako, 2011.
3.Internet resource EC TsOR
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