Yank can be thought as a force in terms of jerk. Force is mass times acceleration. Similarly, Yank is mass times jerk. It is also the derivative of the force. However, when an object is moving near the speed of light, a force is often written as the derivative of momentum. In this case, Yank is the rate of change of the derivative of momentum.
Jerk is used in engineering, particularly in making roller coasters. Weak objects such as people can be damaged by high acceleration or high jerk.
Also, jerk must be thought in the process of making any product. Sudden change in acceleration means very large jerk. Extent of exposure to jerk is often a good predictor of the rate of deterioration of tools while in normal use; it corresponds better to the appearance of metal fatigue among other modes of failure.
Electric current
An electric current is a flow of electric charge. The equation of current is:
The SI unit of electric current is the ampere (A). This is equal to one coulomb of charge in one second.
Current can be found in wires, batteries, and lightning.
In conducting materials, some electrons are very loosely bound to the atoms of the material. When large amounts of these atoms come together, there is a sort of electron cloud that "hovers" near the atoms of the material. If you examine a cross-section of the piece of conducting material, the electrons will move very quickly through it. This motion is caused by temperature, and electrons flowing in one direction tend to equal the electrons flowing from the other direction, so this is not what causes current to flow. Electrons flow from one atom to another, a process has been compared to the passing of water buckets from one person to another in a bucket brigade.
When an electric field is put on the wire, the electrons respond almost instantly by drifting slightly in the opposite direction of the field. They gain energy from the field, which is lost very quickly when they bump into other electrons in the material. As long as the field is in place, however, the electrons will gain back that energy that they lost, and the process will continue. This "jolt" that electrons receive from the electric field is the source of current, not the overall flow of electrons themselves. From this discussion, we can see two things that current is "not":
When current is flowing in a wire circuit, it accelerates when there is no resistance in the circuit. Resistors are used to increase resistance in the circuit so it slows down the current. The relationship between resistance, current, and voltage (another part of the circuit) is shown by Ohm's law.
Inbreeding
Inbreeding is a term in genetics, meaning the crossing (mating) of closely related animals or plants. Self-fertilisation in plants is the most extreme kind of inbreeding. It is quite widespread in plants which carry both male and female flowers on the same plant. Inbreeding is the opposite of outcrossing, which is the mating of unrelated members of the same species. The combination of inbreeding and outcrossing is a standard method of artificial selection.
Other terms are inbred strain, a group of organisms so inbred that they have little or no genetic variation, and inbreeding depression, which is the decreased fitness (usually lack of fertility and early illness and death) brought about by inbreeding.
For human beings, inbreeding is destructive, and almost all cultures have an incest taboo. For example, many prohibit marriage between first cousins, and most prohibit it for closer family members.
Loss of genetic variation means that many gene loci that were heterozygous are now homozygous. The result of both genes at a locus being mutant can be serious.
The most intense form of inbreeding is the self-fertilisation in an hermaphrodite, in which the proportion of heterozygotes is halved in each generation. Aa x Aa (100%) gives 1 AA: 2 Aa; 1 aa (50%), and so on. A similar effect takes twice as long with brother-sister mating, and longer still with mating in very small isolated groups. The latter situation is famous because Sewall Wright did his calculations for just such groups, and he called the process genetic drift. Genetic drift and inbreeding are closely related concepts.
The degree of inbreeding can be measured in various ways. A simple test for mammals is the exchange of skin grafts. If the grafts are not rejected, the animals must be nearly identical genetically. Skin grafts can be successfully exchanged between rats in standard laboratory strains, and between cheetahs caught in the wild.
Why is it that inbreeding brings about a loss of viability? There are two answers, and both seem to be true. The first is that a group with little genetic variation is vulnerable to environmental challenges: infections, sudden climate events, predators. Small groups are vulnerable to chance events in any case, but with no heritable variability they are even more vulnerable.
The second explanation is genetic. Some of the homozygous genes will be "deleterious recessives" which would normally be shielded by a dominant allele. Also, there are some loci where the heterozygote is inherently fitter than either homozygote. If so, inbreeding will automatically cause a loss of vigour.
Many plant species do self-pollination in the wild, but the great majority have occasional outcrossing. This provides them with sufficient variety for their survival.
Cambridge
Cambridge is a city in England. It is north of London. The city is famous for its university, the University of Cambridge, which is thought to be one of the best universities in the world. The university has a hospital (Addenbrooke's Hospital), laboratory (Cavendish Laboratory), chapel (King's College Chapel) and library (Cambridge University Library). There is also a Central Library in Cambridge, on the first floor of the Grand Arcade, St Andrew's Street.
There are 108,863 people living in Cambridge, of which 22,153 are students. There are lots of smaller towns and villages around Cambridge.
The city has lots of parks and is next to the river Cam - the city's name "Cambridge" means "bridge over the Cam."
Adventures of Huckleberry Finn
Adventures of Huckleberry Finn is a book written by Mark Twain, published in 1884. It is a sequel to his earlier book, "Tom Sawyer".
After "The Adventures of Tom Sawyer", Huck was adopted by the widow Douglas who wants to “civilize” him and so he joined Tom’s band of robbers.
One day, Huck’s father Pap, a violent drunkard, appears in St. Petersburg. When a new judge arrives, Pap gains custody of his son and moves to a cabin on the other side of the river. Huck is kept locked but fakes his own death and hides on Jackson’s Island, a small island on the river. There he meets Miss Watson’s black slave Jim who ran away.
When they find a raft, they decide to go to a free state. After a storm, a house is floating down the river and they enter it and grab what they can. Inside, there is a dead man shot in the back and Jim prevents Huck from seeing the dead man’s face.
Huck dresses as a girl and returns to town because he wants to hear what’s going on in town. A woman tells that Jim is considered to be Huck’s murderer. Moreover, she is suspicious about Huck’s true sex and reveals that he is a boy. Huck returns to the island and together with Jim he flees downriver.
After some time on the river, they are separated by a passing steaming boat and Huck meets the Grangerfords, a rich family. He befriends with Buck Grangerford who is about his age. The Grangerfords are in a 30-year feud against the Shepherdsons, another rich family along the Mississippi. When a conflict breaks out, all Grangerford males are killed. Huck can escape and reunites with Jim. Together they float further downriver.
Later, they rescue two con men who join the boys on their journey. They pull several scams along the river. Once, they pretend to be a dead man’s brothers and escape after their true identities are revealed.