Using the Kick Disc Hovercraft to Teach Introductory Physics Concepts in Kinematics and Dynamics By Nils Sorensen Course PH690 Professor Dr MacIsaac Using a Kick Disc to Teach Introductory Physics Abstract The Kick Disc is a small rechargeable hovercraft that provides advantages for teaching introductory physics students the ideas of kinematics and dynamics This paper will introduce a few activities for teachers that use the Kick Disc as the vehicle for discovery The activities described focus mainly on kinematics with some references to beginning dynamics Hovercraft History The idea of Air Cushion Vehicles Hovercraft originated with a British engineer John Isaac Thornycroft who worked on ways to reduce hull friction using air This led him to hydrofoils rather than what we think of as hovercraft floating on a cushion of air but it did however depend on placing air between water and a boat s hull During World War I the coastal defense boats that he QuickTime and a developed were achieving TIFF Uncompressed decompressor are needed to see this picture speeds of up to 45 miles per hour The first air cushion vehicle was produced by a Finnish engineer DI Toivo J Kaario in the 1930 s but it never received the funding required for development Real development took place in the 1950 s in England Christopher Cockerell purchased existing US patents and developed the hovercraft so that in 1959 one of his craft crossed the Channel between France and England Today hovercrafts are best known as car ferries between England and the Continent but they are more widely used in marine rescue because of their ability to move easily over flat beach as well as water The ability of air cushion vehicles to move heavy loads over nasty terrain such as swamps mud flats or smooth ice were not appreciated until the 1970 s Hovercraft in Physics Instruction Hovercraft in physics instruction may have originated in the 1960 s with PSSC Physical Science Study QuickTime and a Committee TIFF Uncompressed decompressor films that used are needed to see this picture machined brass discs pucks with what appeared to be a toilet tank float machined into the top surface The tank was filled with dry ice and tightly corked The carbon dioxide gas generated by the warmed dry ice escaped through a small hole that connected the tank with the bottom of the disc These discs floated effortlessly over horizontal glass surfaces In more recent times these PSSC films have been resurrected and achieved some popularity as a part of the program Physics Cinema Classics These films are helpful but do not put physics into the hands of the students who need direct experience with these materials and situations The PSSC low friction discs were never developed and sold by science education supply houses for the simple reason that they were too expensive for schools to afford They had the additional liability of requiring a ready supply of dry ice It was obvious however that there was an interest in developing low friction devices for physics education because a number of them appeared on the market in the 1970 s One of these was very similar to the PSSC system but the puck was hard plastic and the dry ice container was replaced with a balloon These were very inexpensive and worked if all you wanted was something that would glide for about 1 meter These did a somewhat convincing job of illustrating the 1st Law Unfortunately in order to get any get up and go the balloon had to be large in comparison to the puck so the balloon bent backwards and sideways in the wind touched the table surface and the puck ceased to glide nicely Recently the plastic puck has been replaced by a Compact Disc but that fails to correct its major problem the balloon QuickTime and a TIFF Uncompressed decompressor are needed to see this picture Another attempt used the same plastic pucks rolling on ball bearing like plastic beads This required a smooth tray preferably glass to restrict the beads and puck something like a pool table restricts pool balls The beads created a low friction surface for objects to roll on Air tracks provided an excellent frictionless surface but required an external air supply that was so noisy it prevented the teacher from effective communication during the lesson The air tracks were also delicate expensive and allowed only linear motion Some teachers with extra cash and lots of space purchased air hockey tables These were fun and effective for demonstrations but did not lend themselves to use by large numbers of students This equipment solution never seemed to catch on Today s favorite low friction device seems to be the Pasco cart These are effective in one dimension and relatively inexpensive Their disadvantage for introducing kinematics and the 1st law is that they are moderately expensive and look like the serious physics equipment that they are This can be off putting at an introductory level QuickTime and a TIFF Uncompressed decompressor are needed to see this picture Behold the Kick Disc an air powered disc that has been introduced into the physics education market in the last two years It looks like a toy and can be used on the floor by teachers doing demonstrations or even better by small groups of students working on their own The discs are relatively cheap 25 and small enough so they can be easily stored The rechargeable battery makes it easy to keep them fully charged so that more consistent operation can be maintained over an entire class period What follows is a guide for teachers to incorporate the kick disc into their physics classes The activities provide teachers with ways to help students investigate kinematics and dynamics as well as offer suggestions on how to assess the learning that has occurred Kick Disc Construction The Kick Disc has a very simple and straightforward construction It is a 6 volt motor with an attached squirrel cage fan This moves air from the top of the puck to the bottom Around the fan assembly is a housing and a rubber bumper The entire structure is very light with a mass of only 183 grams without the battery and 300 grams including the 6 volt rechargeable battery Diameter 18 5 cm 7 25 in A Kick Disc base with 6 volt motor wired with a switch on the bottom not shown The grids provide air flow downward and out of the disc 112 grams with the motor B The rubber bumper that protects the plastic from impact 11 grams C The top of the disc with the air intake located in the very center 48 grams D The
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