Question by ameasureoflife: Help with physics- tension and compression?
I understand the concepts behind tension and compression, but I have trouble identifying which one is which in diagrams and such. So, if you have point A and there are 3 forces that join in this point A, how could you identify which ones are working in compression/tension? They all seem like they could be either.
Answer by David Dodeca
First read the wikipedia article on the free body diagram.
Now if there are two equal and opposite forces and they “point at” the free body, it is under compression. If they are pointing away from the body they are creating tension.
Concerning the three forces described above if they are all point toward the object, the object is under compression.
Add your own answer in the comments!
Elias Ashomole, antiquary, whose collection was the basis for the Ashmolean Museum
Image by lisby1
Elias Ashmole (23 May 1617 – 18 May 1692), was a celebrated English antiquary, politician, officer of arms, astrologer and student of alchemy. Ashmole supported the royalist side during the English Civil War, and at the restoration of Charles II he was rewarded with several lucrative offices.
Ashmole was an antiquary with a strong Baconian bent for the study of nature. His library reflects his intellectual outlook, including works on English history, law, numismatics, chorography, alchemy, astrology, astronomy, and botany. Although he was one of the founding members of the Royal Society, a key institution in the development of experimental science, his interests were antiquarian and mystical as well as scientific. He was an early Freemason, although the extent of his involvement and commitment is unclear.
Throughout his life he was an avid collector of curiosities and other artifacts. Many of these he acquired from the traveller, botanist, and collector John Tradescant the younger. Ashmole donated most of his collection, his antiquarian library and priceless manuscripts to the University of Oxford to create the Ashmolean Museum.
Ashmole was born in Breadmarket Street, Lichfield, Staffordshire. His family had been prominent, but its fortunes had declined by the time of Ashmole’s birth. His mother, Anne, was the daughter of a wealthy Coventry draper, Anthony Bowyer, and a relative of James Pagit, a Baron of the Exchequer. His father, Simon Ashmole (1589–1634), was a saddler, who had served as a soldier in Ireland and Europe. Elias Ashmole attended Lichfield Grammar School and became a chorister at Lichfield Cathedral. In 1633, he went to live in London as companion to Pagit’s sons, and in 1638, with the help of Pagit, he became a solicitor. He enjoyed a successful practice in London, and married Eleanor Mainwaring (1603–1641), a member of a poor but aristocratic family, who died, while pregnant, only three years later on 6 December 1641. Still in his early twenties, Ashmole had taken the first steps towards status and wealth.
Ashmole supported the side of Charles I in the Civil War. At the outbreak of fighting in 1642, he left London for the house of his father-in-law, Peter Mainwaring, at Smallwood in Cheshire. There he lived a retired life until 1644, when he was appointed King’s Commissioner of Excise at Lichfield. Soon afterwards, at the suggestion of George Wharton, a leading astrologer with strong court connections, Ashmole was given a military post at Oxford, where he served as an ordnance officer for the King’s forces. In his spare time, he studied mathematics and physics at his lodgings, Brasenose College. There he acquired a deep interest in astronomy, astrology, and magic. In late 1645, he left Oxford to accept the position of Commissioner of Excise at Worcester. Ashmole was given the additional military post of Captain in Lord Astley’s Regiment of Foot, part of the Royalist Infantry, though as a mathematician, he was appointed to artillery positions. He seems never to have participated in any actual fighting.
After the surrender of Worcester to Parliamentary forces in July 1646, he retired again to Cheshire. Passing through Lichfield on his way there, he learnt that his mother had died just three weeks before of the plague. During this period, he was admitted as a Freemason. His diary entry for 16 October 1646 reads in part: "I was made a Free Mason at Warrington in Lancashire, with Coll: Henry Mainwaring of Karincham in Cheshire." Although there is only one other mention of Masonic activity in his diary he seems to have remained in good standing and well-connected with the fraternity as he was still attending meetings in 1682. On 10 March that year he wrote: "About 5 H: P.M. I received a Sumons to appeare at a Lodge to held the next day, at Masons Hall London." The following day, 11 March 1682, he wrote: "Accordingly, I went … I was the Senior Fellow among them (it being 35 yeares since I was admitted) … We all dyned at the halfe Moone Taverne in Cheapeside, at a Noble Dinner prepaired at the charge of the New-accepted Masons." Ashmole’s notes are one of the earliest references to Freemasonry known in England, but apart from these entries in his autobiographical notes, there are no further details about Ashmole’s involvement.
In 1646–47, Ashmole made several simultaneous approaches to rich widows in the hope of securing a good marriage. In 1649, he married Mary, Lady Mainwaring (daughter of Sir William Forster of Aldermaston), a wealthy thrice-widowed woman twenty years his senior. She may have been a relative by marriage of his first wife’s family and was the mother of grown children. The marriage took place over the opposition of the bride’s family, and it did not prove to be harmonious: Lady Mainwaring filed suit for separation and alimony but it was dismissed by the courts in 1657. The match did, however, provide Ashmole with her first husband’s estates centred on Bradfield in Berkshire which left him wealthy enough to pursue his interests, now including botany and alchemy, without concern for his livelihood. He arranged for his friend Wharton to be released from prison and appointed him to manage the estates.
During the 1650s, Ashmole devoted a great deal of energy to the study of alchemy. In 1650, he published Fasciculus Chemicus under the anagrammatic pseudonym James Hasholle. This work was an English translation of two Latin alchemical works, one by Arthur Dee, the son of John Dee. In 1652, he published his most important alchemical work, Theatrum Chemicum Britannicum, an extensively annotated compilation of metaphysical poems in English. The book preserved and made available many works that had previously existed only in privately held manuscripts. There is little evidence that Ashmole conducted his own alchemical experiments. He appears to have been a collector of alchemical writings and a student of alchemy rather than an active practitioner, and refers to himself as a pupil of William Backhouse. His final alchemical publication was The Way to Bliss in 1658, but thereafter his interest seems to wane in favour of his other pursuits. Ashmole promoted the use of therapeutic remedies drawing on both Galenic and Paracelsian principles, and his works attempt to merge the two schools. The Way to Bliss recommends ways to prevent illness: a balanced diet, moderate exercise and enough sleep. His works were avidly studied by other natural philosophers, such as Isaac Newton.
Ashmole met the botanist and collector John Tradescant the younger around 1650. Tradescant had, with his father, built up a vast and renowned collection of exotic plants, mineral specimens and other curiosities from around the world at their house in Lambeth. Ashmole helped Tradescant catalogue his collection in 1652, and, in 1656, he financed the publication of the catalogue, the Musaeum Tradescantianum. In 1659, Tradescant, who had lost his only son seven years earlier, legally deeded his collection to Ashmole. Under the agreement, Ashmole would take possession at Tradescant’s death. When Tradescant died in 1662, his widow, Hester, contested the deed, claiming her husband had signed it when drunk without knowing its contents, but the matter was settled in Chancery in Ashmole’s favour two years later. Hester was to hold the collection in trust for Ashmole until her death. Ashmole’s determined aggressiveness in obtaining the Tradescant collection for himself has led some scholars to consider that Ashmole was an ambitious, ingratiating social climber who stole a hero’s legacy for his own glorification.
In 1669, Ashmole received a Doctorate in Medicine from the University of Oxford. He maintained his links with the University and, in 1677, Ashmole made a gift of the Tradescant Collection, together with material he had collected independently, to the University on the condition that a suitable home be built to house the materials and make them available to the public. Ashmole had already moved into the house adjacent to the Tradescants’ property in 1674 and had already removed some items from their house into his. In 1678, in the midst of further legal wrangling over the Tradescant collection, Hester was found drowned in a garden pond. By early 1679, Ashmole had taken over the lease of the Tradescant property and began merging his and their collections into one. The Ashmolean Museum was completed in 1683, and is considered by some to be the first truly public museum in Europe. According to Anthony Wood, the collection filled twelve wagons when it was transferred to Oxford. It would have been more, but a large part of Ashmole’s own collection, destined for the museum, including antiquities, books, manuscripts, prints, and 9000 coins and medals, was destroyed in a disastrous fire in the Middle Temple on 26 January 1679. As a result of the fire, the proportion of the collection derived from the Tradescants was larger than originally anticipated and in the opinion of Professor Michael Hunter this misfortune has contributed to criticisms that Ashmole took an unfair share of the credit in assembling the collection at the expense of the Tradescants.
In 1678, Ashmole stood as a candidate in a by-election for the Lichfield borough parliamentary constituency caused by the death of one of the two incumbent members. During Ashmole’s campaign his cousin, Thomas Smalridge, who was acting as a kind of campaign manager, fell ill and died. Ashmole did not visit the constituency, and, as Ashmole’s own horoscope had predicted, he lost the election. He also put himself forward as a candidate in the general election of 1685. Surviving documents indicate that he was the most popular candidate, but after King James II requested he stand down (in an age when monarchs were likely to interfere with parliamentary elections), Ashmole did so. On election day, all the votes cast for Ashmole, instead of being declared invalid, were declared as votes for the King’s candidate, and only as a result of this ruse was the candidate favoured by the Court (Richard Leveson) elected.
Ashmole’s health began to deteriorate in the 1680s and, though he would hold his excise office throughout the reign of James II and retained it after the Glorious Revolution until his death, he became much less active in affairs. His home cures included hanging three spiders around his neck which "drove my Ague away". He began to collect notes on his life in diary form to serve as source material for a biography; although the biography was never written, these notes are a rich source of information on Ashmole and his times. He died at his house in Lambeth on 18 May 1692, and was buried at St. Mary’s Church, Lambeth on 26 May. Ashmole bequeathed the remainder of his collection and library to Oxford for the Ashmolean Museum. Two-thirds of his library now resides in the Bodleian at Oxford; its separation from the museum collection in the Victorian era contributed to the belief that Ashmole designed the museum around the Tradescant collection, rather than his own. Ashmole’s widow, Elizabeth, married a stonemason, John Reynolds, on 15 March 1694. They had no children and on her death seven years later the house and lands in Lambeth passed into Reynolds’s hands.
Michael Hunter, in his entry on Ashmole for the Oxford Dictionary of National Biography, concluded that the most salient points of Ashmole’s character were his ambition and his hierarchical vision of the world—a vision that unified his royalism and his interests in heraldry, genealogy, ceremony, and even astrology and magic. He was as successful in his legal, business and political affairs as he was in his collecting and scholarly pursuits. His antiquarian work is still considered valuable, and his alchemical publications, especially the Theatrum Chemicum Britannicum, preserved many works that might otherwise have been lost. He formed several close and long-lasting friendships, with the astrologer William Lilly for example, but, as Richard Garnett observed, "acquisitiveness was his master passion".