Research team develops aqueous rechargeable batteries based on zinc anodes
Can we survive three minutes without air or three days without water? How about without batteries? Imagine not having a battery for three hours.
Nov 2, 2022
0
139
Energy & Green Tech
Can we survive three minutes without air or three days without water? How about without batteries? Imagine not having a battery for three hours.
Nov 2, 2022
0
139
Business
Elon Musk said Wednesday that Twitter will not allow anyone who has been kicked off the site to return until it sets up procedures on how to do that, a process that will take at least a few weeks.
Nov 2, 2022
0
16
Hardware
Materials scientists Nicole Kleger and Simona Fehlmann have developed a 3D printing process for creating salt templates that they can fill with other materials. One area of application is the creation of highly porous lightweight ...
Oct 14, 2022
0
98
Energy & Green Tech
TNO, TU Eindhoven, imec and TU Delft, partners in Solliance, joined forces to further push the conversion efficiency of tandem solar cells to beyond the limits of today's commercial photovoltaic (PV) modules. For the first ...
Sep 27, 2022
0
219
Energy & Green Tech
Harvard's Office of Technology Development has granted an exclusive technology license to Adden Energy, Inc., a startup developing innovative solid-state battery systems for use in future electric vehicles (EVs) that would ...
Sep 3, 2022
1
46
Computer Sciences
As telemedicine has grown more popular, so have devices that allow people to measure their vital signs from home and transmit the results by computer to their doctors. Yet in many cases, obtaining accurate remote readings ...
Aug 24, 2022
0
50
Electronics & Semiconductors
A joint research team in Korea succeeded in identifying the reaction principle of the high-selectivity gas sensing material and developing the world's first multi-response high-selectivity gas sensor that can simultaneously ...
Aug 22, 2022
0
6
Business
Telexistence Inc. and FamilyMart Co. are rolling out a fleet of AI-driven robots to restock shelves in 300 convenience stores across Japan.
Aug 10, 2022
0
23
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
0
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
0
34
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