नवीनतम वीडियो

Teacherflix
3 विचारों · 2 वर्षों पहले

For more information:

http://www.7activestudio.com
info@7activestudio.com

http://www.7activemedical.com/
info@7activemedical.com

http://www.sciencetuts.com/
7activestudio@gmail.com

Contact: +91- 9700061777,
040-64501777 / 65864777

7 Active Technology Solutions Pvt.Ltd. is an educational 3D digital content provider for K-12. We also customise the content as per your requirement for companies platform providers colleges etc . 7 Active driving force "The Joy of Happy Learning" -- is what makes difference from other digital content providers. We consider Student needs, Lecturer needs and College needs in designing the 3D & 2D Animated Video Lectures. We are carrying a huge 3D Digital Library ready to use.

Good sources of energy:
• What is a good source of energy?
• Energy output per unit volume:
• The energy output per unit volume (or mass) of good source of energy should be high. The gas in LPG cylinder can be used by family of average size to cook food for about a month. To cook same amount of food using wood, we need a roomful of wood.
• Steady availability: The energy source should be available readily and for a long time.
• Safe and easy to use: The source of energy has to be safe and easy to use, A fuel that produces a lot of smoke is not a good source of energy, since it is not safe for people’s health. A nuclear power plant is not easy to build and operate.
• Easy to store and transport: Most common sources of energy such as coal, petrol, and LPG need to transport to users from their points of production.
• Economical: The source of energy has to be economical. Hydrogen is excellent fuel. But it is not widely used as it is costly to produce, store and transport it.
• What is a good fuel?
• How much heat does it release on burning?
• It should not produce a lot of smoke.
• The fuel should be available easily.

Teacherflix
4 विचारों · 2 वर्षों पहले

Matter is made up of atoms.
An atom is subdivided into protons, neutrons, and electrons.
The proton and neutron are found in the center of the atom and make up the nucleus.
The negatively charged particles called the electrons are found orbiting the atom.
The orbit of an electron is described as an electron cloud.

Transcript: http://www.moomoomathblog.com/....2021/05/atom-explain

Teacherflix
4 विचारों · 2 वर्षों पहले

Live from the Nuclear Energy Assembly, NEI President and CEO Maria Korsnick presented the industry’s policy priorities and provided perspective on the future of nuclear energy. This is a once-in-a-generation moment defined by demand for carbon-free, reliable nuclear energy.

Teacherflix
4 विचारों · 2 वर्षों पहले

Teacherflix
6 विचारों · 2 वर्षों पहले

Climate change is one of the most pressing issues of our time — and schools have a sizable environmental impact. There are nearly 100,000 public K-12 schools in the United States occupying 2 million acres of land and producing 53,000 tons of food waste. Schools operate one of the largest mass transportation fleets in the country with 480,000 school buses, and they are one of the largest public energy consumers.

We’ll talk with national education leaders — members of an Aspen Institute bipartisan commission that recently released a K12 Climate Action Plan – about how the education sector can be a force toward climate solutions and environmental justice. Join us to talk about how schools and educators can help prepare young people to envision and work toward a more sustainable, resilient, and equitable society.

Speakers:
• John King, Jr., President and CEO, The Education Trust; former U.S. Secretary of Education
• Pedro Martinez, CEO, Chicago Public Schools
• Becky Pringle, President, National Education Association

Moderator: Jennifer Cheatham, Faculty Co-Chair, Education Leadership, Organizations, and Entrepreneurship (ELOE), Harvard Graduate School of Education

Welcome: Bridget Long, Dean and Saris Professor of Economics, Harvard Graduate School of Education

***
The Askwith Education Forum brings leading voices from across the field of education (and beyond) to HGSE for rich and spirited conversations about issues affecting schools, universities, families, and communities.

--

Harvard Graduate School of Education Website: http://www.gse.harvard.edu
Follow us on Instagram: https://www.instagram.com/harvardeducation/
Like us on Facebook: https://www.facebook.com/HarvardEducation/
Follow us on Twitter: https://twitter.com/hgse

Since its founding in 1920, the Harvard Graduate School of Education has been training leaders to transform education in the United States and around the globe. Today, our faculty, students, and alumni are studying and solving the most critical challenges facing education: student assessment, the achievement gap, urban education, and teacher shortages, to name just a few. Our work is shaping how people teach, learn, and lead in schools and colleges as well as in after-school programs, high-tech companies, and international organizations. The HGSE community is pushing the frontiers of education, and the effects of our entrepreneurship are improving the world.

Teacherflix
3 विचारों · 2 वर्षों पहले

Download SCIENCETUTS App to Access 120+ hours of Free content.

For more information:


http://www.7activestudio.com
info@7activestudio.com

http://www.7activemedical.com/
info@7activemedical.com

http://www.sciencetuts.com/


Contact: +91- 9700061777,
040-64501777 / 65864777


7 Active Technology Solutions Pvt.Ltd. is an educational 3D digital content provider for K-12. We also customise the content as per your requirement for companies platform providers colleges etc . 7 Active driving force "The Joy of Happy Learning" -- is what makes difference from other digital content providers. We consider Student needs, Lecturer needs and College needs in designing the 3D & 2D Animated Video Lectures. We are carrying a huge 3D Digital Library ready to use.

energy released during a nuclear reaction as a result of fission or fusion Also called atomic energy. nuclear energy in Science Expand. nuclear energy. The energy released by the nucleus of an atom as the result of nuclear fission, nuclear fusion, or radioactive decay.

When an atom of nuclear fuel (uranium) absorbs a neutron, the uranium will fission into two smaller atoms (waste) and release one to three neutrons. The kinetic energy of the waste is used to heat the water for the steam turbine. The neutrons are used to fission the next lot of uranium atoms and the process continues.

Teacherflix
5 विचारों · 2 वर्षों पहले

This physics video explains the concept of nuclear fission reaction by illustrating an example of nuclear fission of Uranium 235 atom. Nuclear Fission produces Nuclear Energy! Nuclear Fission is a type of Nuclear Reaction where a heavy nucleus splits into lighter nuclei and releases an enormous amount of energy! We look at Einstein's Equation: E = mc2 and how it applies to Nuclear Reactions.
#HowItWorks #NuclearFission #NuclearEnergy #Class12 #K12 #Class10

Chapters:
0:00 What is nuclear fission?
0:17 how does nuclear fission work?
0:22 Quick look at the Nuclear History
1:14 Atomic Structure
1:43 U235 nuclear fission animation
2:34 nuclear fission example

Nuclear fission is nuclear reaction process in which nucleus, when bombarded with a neutron, splits into smaller parts, often producing free neutrons, and releasing a very large amount of energy. One of the most important applications of nuclear fission reactions in creating chain reactions.

Teacherflix
1 विचारों · 2 वर्षों पहले

For more information:

http://www.7activestudio.com
info@7activestudio.com

http://www.7activemedical.com/
info@7activemedical.com

http://www.sciencetuts.com/
7activestudio@gmail.com

Contact: +91- 9700061777,
040-64501777 / 65864777

7 Active Technology Solutions Pvt.Ltd. is an educational 3D digital content provider for K-12. We also customise the content as per your requirement for companies platform providers colleges etc . 7 Active driving force "The Joy of Happy Learning" -- is what makes difference from other digital content providers. We consider Student needs, Lecturer needs and College needs in designing the 3D & 2D Animated Video Lectures. We are carrying a huge 3D Digital Library ready to use.


Chain Reaction in Nuclear Fission: When slow neutrons are bombarded on uranium, each uranium nucleus is broken in to two almost equal parts and along with it enormous energy and two or three trash neutrons are emitted. If the conditions are favorable, these neutrons take part in the fission.This leads to a chain of nuclear fissions which continues till the whole of the Uranium is consumed. Thus the energy produced keep on multiplying.We have seen that about 200 MeV MeV- mega electron volts of energy is released due to fission of 1 Uranium nucleus. In this chain reaction, the number of nuclei undergoing fission increases very rapidly, hence the energy produced acquires an enormous amount very soon."The chain reaction is a series of nuclear fissions in which the neutrons produced in each fission cause additional fissions."This chain reaction liberate tremendous amount of energy within short interval of time. But sustaining a self--propagating chain reaction is not easy in practice, because the progressive chain reaction is inhibited due to the following reasons.A Ordinary uranium consists of three isotopes 92U238 92 Uranium 238, 92U236 92 Uranium 236 and 92U235 92 Uranium 235. The major part of ordinary uranium is the isotope 92U238 92 Uranium 238 the remaining are rare. Now, 92U238 92 Uranium 238 can be fissioned only with fast neutrons 1 MeV while 92U235 can be fissioned with slow as well as slow and fast neutrons. Neutrons having energy less than 1 MeV are absorbed by 92U238 through these low energy neutrons can take part is the fission of 92U235 but the probability of their absorption by U238 is much more. Thus the fresh neutrons released in the fission of ordinary uranium being absorbed by U238 are not able continue the chain reaction. This difficulty can be removed in the following two ways: The lighter isotope U235 can be separated from the ordinary uranium by diffusion method. The fission of U235 is now possible by neutrons of any energy high or low. So chain reaction continuous as shows in above.The second way is to slow down the neutrons by any method. So that their energy remains 0.03 eV This can be achieved with help of moderators, which reduce the speed of neutrons very rapidly. Graphite and heavy water are good moderators.The second difficulty in maintaining the chain reaction is that the fast neutrons released by the fission of U235 travel a distance of about 10 centimeter in the substance before they are slow down and fission other nuclei.Therefore, to continue the chain--reaction, the size of the fissionable substance should be bigger than a certain critical size.

Teacherflix
4 विचारों · 2 वर्षों पहले

The American Nuclear Society, in conjunction with Discovery Education, created a new K-12 STEM education program that started in middle schools across the nation in the fall of 2018. Be sure to check out www.NavigatingNuclear.com and watch the virtual field trip to Palo Verde starting Monday, October 15, 2018.

Teacherflix
5 विचारों · 2 वर्षों पहले

Navigating Nuclear: Energizing Our World fills a void for exciting, fact-based resources that explore nuclear process and the most current technologies that use them. Created by the American Nuclear Society, Discovery Education, and the U.S. Department of Energy, Office of Nuclear Energy, Navigating Nuclear makes the complex nuclear world easier to understand in addition to making nuclear education for K-12 students inspiring—and fun!

For more information, visit https://www.ans.org/nuclear/navigatingnuclear/

#nuclear #nuclearenergy #AmericanNuclearSociety #nuclearscience #science #nuclearengineering #nuclearmedicine #atomic #reactors #fission #fusion #ANS #nuclearpower #nuclearpowerplant #advancednuclear #energy #cleanenergy #decarbonization #climatechange #climatecrisis #environment #engineering #technology #K12 #STEMed #stemeducation #workforcedevelopment #education #utilities

Teacherflix
3 विचारों · 2 वर्षों पहले

Nuclear Fusion | Fusion energy explained with Hydrogen atom example | Physics animation video

In this video we will understand how to or more nucleons merge or fuse together to create something more powerful and meaningful.
Let us first understand the meaning of the word NUCLEAR FUSION, Nuclear meaning the process which involves Nucleus and Fusion in English means two or more entities coming together or merging together to form one single entity.
So, nuclear fusion can be simply defined as the fusion or Combination of Nuclei. Scientifically, Nuclear Fusion can be defined as a nuclear reaction, in which lighter nuclei are combined together to form heavier product nuclei with the release of enormous amount of energy.
Lighter Nuclei such as Lithium and Helium when combined together form a Heavier Nucleus. The mass of heavier nucleus is less than the initial reacting nuclei. The word 'heavier' here is phrased in terms of energy released, which is usually enormous, rather than mass. Therefore the law of conservation of energy is satisfied.
Consider the example of two hydrogen nuclei combining to form a deuterium.
The chemical equation for this reaction is1 1H + 1 1H → 2 1H + 0 +1e + 00 v.
Here, one Hydrogen atom combines with another Hydrogen atom giving Deuterium, one Positron and one Neutrino. This Deuterium in turn combines with another Hydrogen nucleus to form a Helium isotope.
That is, 21H + 1 1H → 3 2He(Helium Isotope)
If two such Helium isotopes are fused together, formation of heavier helium takes place.
In other words, 3 2He + 3 2He → 4 2He + 21 1H
These 3steps of nuclear process, where four protons are fused together to form a heavier 4 2He nucleus and enormous amount of energy is a nuclear fusion reaction.
The chemical equation for this nuclear fusion is:
41 1H → 4 2He + 2 0+1e + 2 00v + Q which is the Energy emitted in the Fusion reaction.
(4 protons when fused together give rise to 2 heavier nucleus, 2 positrons, 2 neutrinos and enormous energy.)
But how is this enormous amount of energy being liberated from such a seemingly simple nuclear reaction. To understand this, let us first calculate the loss of mass in the process.
The starting mass is that of four protons, that is 4 X 1.0078 = 4.0312amu, but the final mass of Helium nucleus is 2me= 4.001506amu.
Therefore the loss of mass is 4.0312 - 4.001506 = 0.0297 amu.
This is equivalent to an energy given by Q = (0.0297amu) X 931,5 Mev/amu =27.67 Mev.
Wow......That is a significant energy release coming from the fusion of 4 protons.
However, in spite of such substantial amounts of energy being released in nuclear fusion reactions, there are no full-time nuclear reactors built so far for fusion reaction as it is very hard to control such enormous energy released.

Teacherflix
3 विचारों · 2 वर्षों पहले

Disciplinary Core Idea PS1C - Nuclear Processes

Paul Andersen explains three major nuclear processes; fusion, fission, and decay. He begins with a brief discussion of the four fundamental forces in nature. He the explains how nuclei can be combined in fusion, divided through fission, and changed through radioactive decay. A discussion of the teaching progression K-12 is also included.


Intro Music Atribution
Title: I4dsong_loop_main.wav
Artist: CosmicD
Link to sound: http://www.freesound.org/peopl....e/CosmicD/sounds/725
Creative Commons Atribution License

All images are either Public Domain or Creative Commons Attribution Licenses:
Evans, NASA Photo taken by either Harrison Schmitt or Ron. Deutsch: „Blue Marble", Die Während Des Fluges Von Apollo 17 Zum Mond Am 7. Dezember 1972 Entstandene Fotoaufnahme Von Der Erde (in Der Zur Besseren Wiedererkennbarkeit Um 180 Grad Gedrehten Version)., December 7, 1972. Smaller version: ftp://nssdcftp.gsfc.nasa.gov/miscellaneous/planetary/apollo/a17_h_148_22727.tiff as linked and thumbnailed by http://nssdc.gsfc.nasa.gov/img....cat/midres/a17_h_148 on http://nssdc.gsfc.nasa.gov/img....cat/html/object_page and converted to JPEG and uploaded by Ed g2s 22:41, 29 December 2004 (UTC) Larger version: http://www.nasa.gov/images/con....tent/115334main_imag as converted to JPEG and published by NASA using Adobe Photoshop CS Windows 13:09, 13 May 2005 and uploaded by Tom 02:25, 31 July 2005 (UTC) Higher-resolution but uglier image: apollo17_earth.tiff as contained by ftp://nssdcftp.gsfc.nasa.gov/photo_gallery/hi-res/planetary/earth/apollo17_earth.tiff.gz and converted to JPEG with 100% quality using Paint.NET v3.5.5 by Jeff G. 06:15, 17 October 2010 (UTC) Higher-resolution image for review: as17_148_22727.jpg received in an email dated Mon, 18 Oct 2010 12:18:10 -0400 from one of the NASA Catalog of Spaceborne Imaging Curators with the text "This is the highest res I have. The original was a photographic 70mm color positive which is part of a group that is being scanned at much higher resolution." This image or video was catalogued by Johnson Space Center of the United States National Aeronautics and Space Administration (NASA) under Photo ID: AS17-148-22727. This tag does not indicate the copyright status of the attached work. A normal copyright tag is still required. See Commons:Licensing for more information. Català | Česky | Deutsch | English | Español | فارسی | Français | Galego | Magyar | Հայերեն | Bahasa Indonesia | Italiano | Македонски | മലയാളം | Polski | Português | Русский | Türkçe | 中文 | 中文(简体)‎ | +/−. http://commons.wikimedia.org/w....iki/File:The_Blue_Ma
"File:All Gizah Pyramids.jpg." Wikipedia, the Free Encyclopedia, March 23, 2013. http://en.wikipedia.org/w/index.php?title=File:All_Gizah_Pyramids.jpg&oldid=488928945.
"File:Deuterium-tritium Fusion.svg." Wikipedia, the Free Encyclopedia. Accessed March 23, 2013. http://en.wikipedia.org/wiki/F....ile:Deuterium-tritiu
"File:GodfreyKneller-IsaacNewton-1689.jpg." Wikipedia, the Free Encyclopedia. Accessed March 23, 2013. http://en.wikipedia.org/wiki/F....ile:GodfreyKneller-I
"File:Keplers Supernova.jpg." Wikipedia, the Free Encyclopedia, March 17, 2013. http://en.wikipedia.org/w/index.php?title=File:Keplers_supernova.jpg&oldid=339667962.
"File:Nagasakibomb.jpg." Wikipedia, the Free Encyclopedia, March 23, 2013. http://en.wikipedia.org/w/index.php?title=File:Nagasakibomb.jpg&oldid=506130783.
"File:Starsinthesky.jpg." Wikipedia, the Free Encyclopedia, March 12, 2013. http://en.wikipedia.org/w/index.php?title=File:Starsinthesky.jpg&oldid=479082988.
"File:The Sun by the Atmospheric Imaging Assembly of NASA's Solar Dynamics Observatory - 20100819.jpg." Wikipedia, the Free Encyclopedia. Accessed March 23, 2013. http://en.wikipedia.org/wiki/F....ile:The_Sun_by_the_A

Teacherflix
4 विचारों · 2 वर्षों पहले

Dorado Learning has an exclusive range of products K-12 products. Our products are already used by over 100,000 students world wide. The range includes K-12 2D and 3D animation library of over 50,000 modules. The modules are structured in a molecular format so that they can be mapped with any curriculum easily.

Teacherflix
3 विचारों · 2 वर्षों पहले

Follow us on https://www.instagram.com/7activestudio/

For more information:

http://www.7activestudio.com
info@7activestudio.com

Contact: +91- 9700061777, 040-66564777

7 Active Technology Solutions Pvt. Ltd. is an educational 3D digital content provider for K-12. We also customise the content as per your requirement for companies platform providers colleges etc. 7 Active driving force "The Joy of Happy Learning" -- is what makes difference from other digital content providers. We consider Student needs, Lecturer needs and College needs in designing the 3D & 2D Animated Video Lectures. We are carrying a huge 3D Digital Library ready to use.


NUCLEAR FISSION: In our earlier session, we have learnt about nuclear process.Now let us learn about chain reaction in the nuclear process.A nuclear process in which a heavy nucleus, when bombarded with neutrons split into two nuclei of nearly equal mass along with release of enormous amount of energy is called as nuclear fission.In the above said process, every neutron can cause fission but along with the fission, it also releases 3 more neutrons on every fission reaction.Every neutron that is released can cause another fission reaction.Thus the three neutrons released in turn releases 9 neutrons.In the similar way, reaction continues and neutrons are built up in geometric progression and fission occurs till total uranium gets exhausted in a chain manner.This process is called as chain reaction and these reactions are called as Self-sustained series of fissions.The chain reaction: is a series of nuclear fissions whereby the neutrons produced in each fission cause additional fissions.There are two stages of chain reactions are there.Uncontrolled Chain reaction. Controlled Chain reaction. Uncontrolled chain reaction:In the chain reaction, there is no control on the number of fissions taking place and such reactions are called uncontrolled chain reaction.In this chain reaction more than one of the neutrons produced in a particular fission cause further fissions. So that the number of fissions increases very rapidly. Therefore an enormous amount of energy is released within a few millionths of a second and is released as a violent explosion. An average energy of about 200MeV Mega electron volts would be release per fission.Thus, an uncontrolled chain reaction can generate an incredible amount of energy within a very short time.This is actually what happens in an 'Atom Bomb'.Controlled chain-reaction:

Teacherflix
1 विचारों · 2 वर्षों पहले

Dr. Baranwal will address four key points about the (1) range of issues facing the existing fleet of nuclear power plants; (2) barriers and opportunities for the deployment and construction of advanced reactors, including small modular reactor designs enabled by the DOE’s Advanced Reactor Demonstration Program; (3) challenges and opportunities in the critical fuel cycle infrastructure; and (4) challenges and opportunities for global competitiveness of U.S. nuclear technology.

Speaker bio

Dr. Rita Baranwal serves as the Assistant Secretary for the Office of Nuclear Energy in the U.S. Department of Energy. Prior to her current role, Dr. Baranwal directed the Gateway for Accelerated Innovation in Nuclear (GAIN) initiative at Idaho National Laboratory.

Dr. Baranwal is a Fellow of the American Nuclear Society. She has a bachelor’s degree from Massachusetts Institute of Technology in materials science and engineering and a master’s degree and Ph.D. in the same discipline from the University of Michigan.

Teacherflix
3 विचारों · 2 वर्षों पहले

How does a nuclear reactor provide energy? What causes a nuclear meltdown? And how do we make this safe?

All of these questions are answered in this 'Radioactivity' video from The Fuse School GCSE / K12.

At Fuse School, teachers and animators come together to make fun & easy-to-understand videos in Chemistry, Biology, Physics, Maths & ICT. Our OER are available free of charge to anyone. Make sure to subscribe - we are going to create 3000 more!

Be sure to follow our social media for the latest videos and information!

Twitter: https://twitter.com/fuseschool
Facebook: https://www.facebook.com/fuseschool
Google+: http://www.gplus.to/FuseSchool
Youtube: http://www.youtube.com/virtualschooluk
Email: info@fuseschool.org
Website: www.fuseschool.org

This video is distributed under a Creative Commons License:
Attribution-NonCommercial-NoDerivs CC BY-NC-ND

Teacherflix
5 विचारों · 2 वर्षों पहले

Nuclear Engineering: http://engineering.purdue.edu/NE
Facebook: http://bit.ly/PurdueNE-Facebook
Twitter: https://twitter.com/PurdueNuclear
Instagram: https://instagram.com/purduenuclear @purduenuclear


#purdue #nuclearengineering #nuclearenergy

Teacherflix
3 विचारों · 2 वर्षों पहले

For accessing 7Activestudio videos on mobile Download SCIENCETUTS App to Access 120+ hours of Free digital content.

For more information:


http://www.7activestudio.com
info@7activestudio.com

http://www.7activemedical.com/
info@7activemedical.com

http://www.sciencetuts.com/


Contact: +91- 9700061777,
040-64501777 / 65864777


7 Active Technology Solutions Pvt.Ltd. is an educational 3D digital content provider for K-12. We also customise the content as per your requirement for companies platform providers colleges etc . 7 Active driving force "The Joy of Happy Learning" -- is what makes difference from other digital content providers. We consider Student needs, Lecturer needs and College needs in designing the 3D & 2D Animated Video Lectures. We are carrying a huge 3D Digital Library ready to use.

Nuclear power plants obtain the heat needed to produce steam through a physical process. This process, called fission, entails the splitting of atoms of uranium in a nuclear reactor. The uranium fuel consists of small, hard ceramic pellets that are packaged into long, vertical tubes.

Teacherflix
1 विचारों · 2 वर्षों पहले

Some people think radiation is a scary word but really is just the movement of particles or waves through space, learn all about nuclear radiation in this GCSE / K12 video.

Get in touch: vsteam@fusion-universal.com
Find out more: http://www.thevirtualschool.com
Follow us: http://www.youtube.com/virtualschooluk
Friend us: http://www.facebook.com/virtualschooluk

Teach the world.

This video is distributed under a Creative Commons License:
Attribution-NonCommercial-NoDerivs
CC BY-NC-ND

Teacherflix
2 विचारों · 2 वर्षों पहले

Download SCIENCETUTS App to Access 120+ hours of Free content.

For more information:


http://www.7activestudio.com
info@7activestudio.com

http://www.7activemedical.com/
info@7activemedical.com

http://www.sciencetuts.com/


Contact: +91- 9700061777,
040-64501777 / 65864777


7 Active Technology Solutions Pvt.Ltd. is an educational 3D digital content provider for K-12. We also customise the content as per your requirement for companies platform providers colleges etc . 7 Active driving force "The Joy of Happy Learning" -- is what makes difference from other digital content providers. We consider Student needs, Lecturer needs and College needs in designing the 3D & 2D Animated Video Lectures. We are carrying a huge 3D Digital Library ready to use.

A boiling water reactor uses 235U, enriched as uranium dioxide, as its fuel. The fuel is assembled into rods housed in a steel vessel that is submerged in water. The nuclear fission causes the water to boil, generating steam.

In a nuclear power reactor, the energy released is used as heat to make steam to generate electricity. (In a research reactor the main purpose is to utilise the actual neutrons produced in the core. In most naval reactors, steam drives a turbine directly for propulsion.)




Showing 655 out of 656