Automation and advanced materials are the 'dream team'
Automated systems combined with new materials will combine as a "dream team" to start a revolution in advanced manufacturing, says a graphene pioneer.
Jul 5, 2022
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15
Engineering
Automated systems combined with new materials will combine as a "dream team" to start a revolution in advanced manufacturing, says a graphene pioneer.
Jul 5, 2022
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15
Internet
With gun control under debate and monkeypox in the headlines, Americans are facing a barrage of new twists on years-old misinformation in their social media feeds.
Jun 10, 2022
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34
Robotics
Blake Resnick was a 17-year-old growing up in Las Vegas when a gunman firing from a Strip hotel window killed 60 people at an outdoor concert.
Jun 8, 2022
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Other
Decommissioning and clean-up are ongoing at the Fukushima Daiichi Nuclear Power Plant (FDNPP); however, many difficult problems remain unaddressed. Chief amongst these problems is the retrieval and management of fuel debris. ...
Jan 25, 2022
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8
Business
Chinese artificial intelligence start-up SenseTime said Monday it was postponing a $767 million initial public offering in Hong Kong after it was blacklisted by the United States over accusations of genocide in Xinjiang.
Dec 13, 2021
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17
Automakers Mercedes-Benz and Stellantis announced agreements with U.S. company Factorial Energy on Tuesday to help develop solid-state battery technology that they hope could make electric cars more attractive to a mass market.
Nov 30, 2021
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14
Internet
As social media giants like Facebook and Twitter come under increasing criticism for how they approach what type of speech is allowed on their platforms, another type of online group navigated similar struggles more than ...
Oct 7, 2021
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3
Engineering
Recognizing fake drugs? Testing water samples ourselves? Checking the quality of air? In the future, it could be possible to do all this using a smartphone in a quick, cost-effective and straightforward way. The process is ...
Jul 1, 2021
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5
Internet
Russia has launched a probe against YouTube for "abusing" its dominant position in the market by making "biased" decisions about comment moderation, a government regulator said on Monday.
Apr 19, 2021
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5
Internet
Cambodia's government moved to exert near-total control over the country's online life Wednesday, setting up a national internet gateway which activists say will stifle freedom of expression and block content via a China-style ...
Feb 17, 2021
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7
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity. In physics, mass (from Ancient Greek: μᾶζα) commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:
Mass must be distinguished from matter in physics, because matter is a poorly-defined concept, and although all types of agreed-upon matter exhibit mass, it is also the case that many types of energy which are not matter—such as potential energy, kinetic energy, and trapped electromagnetic radiation (photons)—also exhibit mass. Thus, all matter has the property of mass, but not all mass is associated with identifiable matter.
In everyday usage, "mass" is often used interchangeably with weight, and the units of weight are often taken to be kilograms (for instance, a person may state that their weight is 75kg). In scientific use, however, the two terms refer to different, yet related, properties of matter. Weight can be zero if no gravitational force is acting but mass can never be zero.
The inertial mass of an object determines its acceleration in the presence of an applied force. According to Newton's second law of motion, if a body of fixed mass M is subjected to a force F, its acceleration α is given by F/M.
A body's mass also determines the degree to which it generates or is affected by a gravitational field. If a first body of mass MA is placed at a distance r from a second body of mass MB, each body experiences an attractive force F whose magnitude is
where G is the universal constant of gravitation, equal to 6.67×10−11 N m2kg-2. This is sometimes referred to as gravitational mass (when a distinction is necessary, M is used to denote the active gravitational mass and m the passive gravitational mass). Repeated experiments since the 17th century have demonstrated that inertial and gravitational mass are equivalent; this is entailed in the equivalence principle of general relativity.
Special relativity shows that rest mass (or invariant mass) and rest energy are essentially equivalent, via the well-known relationship (E=mc2). This same equation also connects relativistic mass and "relativistic energy" (total system energy). These are concepts that are related to their "rest" counterparts, but they do not have the same value, in systems where there is a net momentum. In order to deduce any of these four quantities from any of the others, in any system which has a net momentum, an equation that takes momentum into account is needed.
Mass (so long as the type and definition of mass is agreed upon) is a conserved quantity over time. From the viewpoint of any single unaccelerated observer, mass can neither be created or destroyed, and special relativity does not change this understanding (though different observers may not agree on how much mass is present, all agree that the amount does not change over time). However, relativity adds the fact that all types of energy have an associated mass, and this mass is added to systems when energy is added, and the associated mass is subtracted from systems when the energy leaves. In such cases, the energy leaving or entering the system carries the added or missing mass with it, since this energy itself has mass. Thus, mass remains conserved when the location of all mass is taken into account.
On the surface of the Earth, the weight W of an object is related to its mass m by
where g is the Earth's gravitational field strength, equal to about 9.81 m s−2. An object's weight depends on its environment, while its mass does not: an object with a mass of 50 kilograms weighs 491 newtons on the surface of the Earth; on the surface of the Moon, the same object still has a mass of 50 kilograms but weighs only 81.5 newtons.
This text uses material from Wikipedia, licensed under CC BY-SA