全國中小學科展

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南非

Road Surbace Reflectivity

The focus of this investigation is on how one might be able to reduce the number of accidents and the risk of accidents on our country’s roads by using more reflective products on or in the roads. The reflective products that were used in experimental processes for this investigation were: glass (both brown and clear in colour); oyster shells; reflective paint containing glass beads; glass beads on their own; armour plated glass and a road reflector. These reflective products were compared to a normal tar road and a concrete road

Swimming Pool safety Device "Baby Buzzer"

Annually several baby’s and toddlers drown. There are safety devices available on the\r market for ex: Safety nets in which toddlers can get strangled. Pool covers that have to be\r taken off when people swim and replaced after they have swam. If they are not replaced\r afterwards, babies could fall in the water and drown. Fences around the pool:- The gate\r could accidentally be left open and the toddler could fall in and drown.

Pulse Jets

I made this jet engine to demonstrate how a pulse jet works and to show were the fundamentals of powered aviation all began. I also made this project to gain more knowledge, due to my interests in engineering and turbines. I would also like to measure the thrust of this model in the future. And hopefully this might inspire other people to use this type of engine in their model aircraft.

Waste Not,Want Not

Many people in South Africa still use open fires for cooking. There is a\r large amount of wasted heat lost by four methods of heat transfer:-\r radiation, convection, conduction and evaporation.\r I constructed a vessel that would reduce heat loss, and focus the heat\r emitted from a fire onto the bottom of a pot. I used materials that were\r cheap and easy to obtain, so that those using open fires would be able to\r construct similar vessels to save energy and reduce pollution.\r The vessels were made up of a standard wire mesh frame that was\r surround by trial coverings, namely tin foil, asbestos rope, industrial foil,\r papier mache, ceramic, and 2 ceiling insulators.\r 5 mls of methylated spirits was burned in each vessel. The temperature\r gain of 100mls of water in a standard pot was recorded. 5 trials on each\r vessel were performed. 2 groups of vessel were found. Those that\r produced high temperature gains, burned quickly, and produced a large\r amount of soot deposits on the pot, and a second group that did the\r opposite.\r I compared the rate of heating from my best vessel to that of a stove as\r well as a microwave oven. Heating from the vessel was faster than that of\r the stove, and slightly slower than the microwave.\r I measured the heat emitted from a fire in a three-dimensional pattern and\r found that the maximal heat was some distance above the flame.\r From these results I devised 12 guidelines that would minimize the\r energy need, and pollution produced, when cooking on an open fire

Art is Science

Cable Stripper

PURPOSE OF THE RESEARCH \r The purpose of this project is to provide a cost-effective and efficient way of \r stripping electrical conductors, with thicknesses of 16mm up to 70mm in diameter, \r of their isolation. The current methods that are available are unsafe and unpractical. \r Therefore this project determines a safe way of stripping cables and also provides a \r new product to improve the worker’s safety during the process of stripping cables. \r PROCEDURES \r The solution can be found by doing research on the types of cable isolations \r currently on the market. By talking to the workers who use these types of tools, and \r strip these types of cables on a daily basis, I can comprehend the problems posed by \r the present methods and provide a solution. \r DATA \r An electrical cable is commonly a conductive wire surrounded by a nonconductive, \r insulation sleeve. In order to splice two cables together or connect the \r cable to an electrical device, the conductive wire inside the sleeve needs to be \r exposed. \r Numerous tools have been developed for slitting and stripping the electrical \r cable in order to expose the said conductive wire. The simplest tool is a knife with \r which the user makes an annular cut in the sheathing. The end portion of the \r sheathing then is pulled away exposing the individually insulated wires and the bare \r ground wire. The knife may also be used to cut away a short portion of the \r insulation at the ends of the wires. During both operations the user has to be \r extremely careful, or else the knife blade may damage the insulation around the \r internal wires and even nick the conductor or he may injure himself. To do so the \r user must first cut away several inches of the plastic sheathing at the end of the \r cable. A short length of the insulation then is removed from around each end of the \r conductors. \r As an alternative to using a knife, various scissors-like wire strippers have been \r developed. Although such scissors-like wire strippers are effective for removing the \r insulation from individual wires within an electrical cable, they are not efficient for \r removing the sheathing from the end of the cable in order to expose the individually \r insulated wires. \r A disadvantage of using a conventional knife and with using the known wire \r stripper is that a cable having a relatively thick insulation sleeve is difficult to strip \r and thus prepare for connections, since conventional wire stripping tools and other \r conventional devices, such as knives or tools with enclosed blades are inefficient for \r stripping thicker cable jackets. \r A further disadvantage of the known wire strippers is that, its basic \r characteristic dictates that the degree of friction between the tool and the wire after \r the insulation has been ringed will be high. This occasions no particular difficulty \r when only a short length of insulation is to be removed from the end of the wire. \r However, when yards and yards of insulation are to be stripped, as may be the case \r when reel ends are to be prepared for scrapping, the conventional wire stripper \r generates so much friction that it cannot be efficiently utilised. \r CONCLUSION \r The developed product enables workers to effectively strip electrical \r conductors without any impeding danger to themselves or the risk of damaging said \r cable. It is cost-effective and saves a lot of time. After several tests of the product no \r problems have been encountered up to this point.

Habit and comparison of the Opistophthalmus pugnax and the Opistophthalmus

To compare the habitat and physical\r differences of two burrowing scorpions, Opistophthalmus pugnax and\r the Opistophthalmus glabrifrons to be found in the Gauteng area\r (South Africa). Although these scorpions’ habitat overlaps, they don’t\r co-occur at the same site.

What really attracts boys to girls

The purpose of this research was to challenge misconceptions about what attracts teenaged boys to girls. It has been observed that some teenaged girls hold stereotypes about boys and believe boys are only attracted to superficial qualities like beautiful hair. The aim is to investigate differences between what girls believe boys find attractive about them and what boys actually find attractive about girls. Hypothesis: There is a significant difference between what teenaged boys find attractive in girls and what teenaged girls think boys find attractive. Procedure Background reading was done to discover which characteristics are commonly used to measure attractiveness among teenagers. A survey questionnaire was used for gathering data. To gather information for the construction of the questionnaire, 4 focus groups were interviewed. The groups were asked to determine indicators of attraction and repulsion. Two separate questionnaires were designed (one for boys and one for girls), based on focus group information, with similar questions which could be used to compare results. Questions were related to personality and looks. The research was representative as 399 teenagers participated in the final survey. Results were collated in Excel tables. Percentages were calculated by using a scientific calculator and Excel. A bivariate analysis was created to examine the main question: ranking qualities that attract boys to girls. A comparison was made between boys’ and girls’ opinions from different age categories. Mean averages were calculated for this question. Other questions were analysed using mode averages translated into percentage of each gender. Graphs were designed using the values calculated. Observations/Data/Results 72% of boys prefer a girl with average looks and an awesome personality but only 37% of girls believed that to be true. The average boys from 12-14, 15-17 and 18-20 year old categories agree that confidence, humour, a nice body, politeness and intelligence are the five most attractive qualities in a girl they would consider dating. The order of these five change across the age groups but are constantly the top five, however confidence and humour always trump a “nice body”. The average 12-14 and 15-17 year old girl overrates a nice body and underrates politeness and intelligence but confidence and humour feature in their top five. The average 18-20 year old girl agrees with the boys priorities. When defining what makes a girl beautiful, 68% of boys highlight personality traits and 59% of boys mentioned physical features. When noting what repulses boys about pretty girls, more than 50% of both sexes agree that smelling bad was most off putting. 52% of boys mentioned taking drugs as unattractive yet only 23% of girls recognized this as repulsive. Conclusions The data supports the hypothesis. Confidence and humour are more important to the average boy than a nice body across all age groups. The younger the girl, the less she understands what attracts boys. 63% of teenaged girls believe that looks are more important to boys than personality. This is clearly not true. 72% of boys value a great personality more highly than good looks.

Trespasser:Farmer or Leopard?

Up the Creek

After an annual swimming rally in the Nahoon river, concerns were raised after several swimmers fell ill, complaining of possible symptoms of mild E.coli infection. Research was hence conducted to determine the following: \r \r \r The Nahoon River is safe for recreational activity in terms of faecal-coliforms and E.coli \r \r \r Whether the amount of rainfall affects these levels. \r \r \r If faecal pollution is present, to determine the possible point sources of the pollution \r \r \r To devise a method that needs no assistance from a laboratory, and could be done in a home environment at low cost. \r \r \r \r Procedures \r Colilert-18, (the reagent) contains nutrients which react to faecal-coliforms and E.coli in the sample. It causes samples to change colour when contamination is present. A dilution method (used by the Kowie Catchment Campaign) was used to test the severity of the contamination. The dilution levels were as follows: 1, 1/10, 1/100 and 1/1000. A control test was also performed. One Colilert capsule was divided among the five samples, which were incubated in a household stove at 37ºC for 18 hours. A sample was collected every four days and after heavy rainfall. \r The results were rated on a severity scale of 0-4, where a two was considered unsafe for recreational activity. If the undiluted sample remained clear, it was ra ted 0, if all the samples changed colour, it was rated as a four. The same rating system was used when fluorescing samples to test for E.coli. The daily rainfall level was compared to the levels of faecal-coliforms and E.coli. \r Conclusion \r As it has high levels of faecal coliforms and E.coli, the Nahoon River is not safe for recreational activity on a daily basis. \r Heavy rainfall causes the levels of E.coli and faecal coliforms to rise. \r The major source of the contamination is a stream entering the river from a newly developed settlement, and not a leaking sewer. \r This experiment has developed cost-effective home environment testing method which could be used in researching other rivers, marine environments, recreational waters and even drinking water by community researc