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Physics of Catapults Essay - 1122 Words

The ballista, or shield piercer, was first developed by the Greeks using the same principles as a bow and arrow. Its primary use was to, as the name suggests, pierce enemy shields, since normal bows lacked the power to do so. Early versions of the ballista include the gastrophetes, which is nothing more than an enlarged bow that can be braced against the users body. http://members.lycos.nl/onager/GastrophetesPic.jpg As time went on ballistas were improved to become larger and more powerful, eventually becoming mounted mechanisms that could be operated by two or more people. The Romans eventually modified them to throw stones, making them more effective in seiges against walled†¦show more content†¦Using this relationship assumes that the force constant is constant, or that moving the arms back 2 meters gives twice the force that moving them back 1 meter would do, which is most likely not correct, but close enough for a general assumption of the force to be made. When the force is applied, the projectile is accelerated to the end of the ballista, at which point it released with a velocity v and an angle q from the horizontal. The velocity can be found using the kinematic equation v2=2ax, where a is the acceleration and x is the length of the ballista that the projectile is accelerated upon. Since F=ma and F in this case is -kd, the equation can be simplified into v2=2-kdx/m. After it is released, the projectile obeys the laws of projectile motion, disregarding air resistance. Therefore, the range of the ballista can be given by the equation R=v2sin2q/g, where g is the accleration due to gravity. Mangonel History The Romans, finding the ballista difficult to construct, simplified the design and created the onager. It had one arm instead of two, and is what is most commonly identified as a catapult today. http://members.lycos.nl/onager/OnagerPic.jpg During the Dark Ages, the French were able to re-invent the onager, and they called it the mangonneau, and it became known in England as the mangonel. MangonelShow MoreRelatedResearch Testing the Shot Distance of the Crossbow, the Catapult, and the Slingshot1103 Words   |  4 Pagesand test different weapons from those eras. I am finding out which shoots the furthest the crossbow, the catapult, or the slingshot and if I do not know how they work, I cannot compare them to each other so I decided to research this. My hypothesis is that the catapult will shoot the furthest and I think that I am right do to previous research by professionals. 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HR problem Free Essays

All employees are continually performance managed and this is looked at when going or promotion so the employees are always putting a lot of effort to get good assessments and appraisals. When many of the employees joined the company they were told that promotion would be available within two years, however this has not been the case. The general management seem not to worry about this lack of motivation and seem to think as long as the employees are making money they will be happy. We will write a custom essay sample on HR problem or any similar topic only for you Order Now Part b Problem Analysis To analyses the problems in this organization we need to look the issue of motivation at work and also the psychological contract between the company and the employee. Arnold et al (1995 cited in Preston 2006 P. 7) suggests that motivation is made up of three components: 1 . Direction: what a person is trying to do 2. Effort: how hard a person is trying 3. Persistence: how long a person continues trying Looking at this suggestion you can see that In the case of the employees they have a key direction In looking for promotion and are putting In a lot of effort to receive good assessments and appraisals. However, they are starting to lack in persistence as they A highly motivated employee will be: o More committed to the business o A more productive worker Happier in their Job A useful theory we can use to look at motivational issues is Mascots hierarchy of needs. Self-actualization Esteem Social (belonging) Safety Physiological Preston (2006 p. 12) states ‘Mason believed that all people are motivated by the same things, but there are different levels of need. When one set of needs in the hierarchy has been met, we work harder to fulfill the next level. ‘ In relation to the problem stated earlier a majority of the employees work hard to achieve the different stages of need, however now they are lacking motivation because they are striving for more ND working harder to achieve more but it is not being made available to them. We can also look at Victor Broom’s expectancy theory he uses the equation x I x V) which looks at the process of motivation. In this case even though the effort being but in by the employees is huge, the outcome they are hoping for (promotion) is not great or non-existent. As promotion is a high priority for these employees they therefore have a lack of motivation. Another motivation theory we can link to this problem is Douglas McGregor (1960) Theory X and Theory Y. In this case the management are obviously Theory X managers only believing employees are motivated by money. The employees will become very disheartened by this as they are trying extremely hard and not being recognized for it. The psychological contract forms part of the unwritten contract and as Preston (2006 pop) states ‘differs from a written contract in that it is concerned with implicit expectations, obligations and promises that both parties believe have been made with regard to what each owes and expects to receive from each other. ‘ The psychological contract covers a lot of areas and has become more important in cent times where the employee expects a lot more from their employer. When joining the company the employees understood that promotion would be available within two years. This was not in the official written contract but was a known promise. Many employees now feel dishonored. They have put in a lot of hard work which they expected would put them well on the road to promotion. These few points are all examples of the psychological contract. In this case it is very weak; this is also a good reason as to why the employees are not motivated. I think this problem could be solved and have produced a few ideas which could help both short term and long term. ; Condiment opportunities The company could offer its employees short term condiment opportunities in a higher position when the man power is stretched and in need of a temporary boost. Even though it is not permanent it may help increase motivation in the short term. In the case on Broom’s theory the promotion they have been working towards will have been made available (if only temporarily) which will increase motivation ; Working in there departments – increase company knowledge There may be a chance to look at letting employees work in different departments short term especially during low season when man power levels needed are not as high. This will benefit both the company and the employee. The business will benefit from the extra knowledge and skills the employee will learn which they will be able to bring back to their original role. The employee will enjoy doing something new and being more challenged therefore increasing motivation. ; Opportunities to work up On certain shifts the manager on duty could delegate his duties to a more Junior employee. This gives the employee the opportunity to learn on the Job whilst being supervised by the manager. This could provide a challenge and more stimulating day at work. Better the relationship between managers and employees Reduce the barriers between general management and the workforce, I. E. Improving and encouraging more fluid communication between each party. This will enable the management to see how dedicated and committed their staff actually are and allow them to have a more personal idea of who their employees are. This would be a start n changing the managers from Theory X to Theory Y managers when looking at Dougl as McGregor theory. How to cite HR problem, Papers