An experimental model for the diagram shown above would be a slide on a table. A smooth object will travel down the slide and land on the floor with a precise measurable distance d. Before materials are named, certain modelling assumption will be made clear.
Modelling Assumptions & Materials
Taking into consideration that resistive forces must be minimal, or omitted altogether, in order for experimental and theoretical results to be compared with accuracy, suitable materials have to be used. Materials must have an appropriate arrangement and qualities to avoid such forces to effect results.
The object that travels down the slide will be modelled as a particle with only one force acting on the object: its weight (mg). Any frictional forces will be ignored in preliminary modelling of the object down the slide. The object must remain rigid throughout the tests. If the object is not rigid, measured distances of its position would be inaccurate. Resistance with air should not influence its path down the slide and through the air before landing at d, with the indoor conditions where the tests will take place. There should no wind resistance present in this environment.
The Slide (inclined plane)
The plane has to be rigid enough to avoid bending when the object is placed on it. The slide must have minimal frictional forces between it and the object, the slide has to be smooth and have a non-grip slippery surface. The rate of acceleration would be affected if the inclined plane the object rested upon was not flat. This would also mean a varying change in q making comparisons infeasible over values of l. The angle of the slope will remain fixed for each set of tests.
The Floor (at d)
This is the surface that stops further downward vertical movement of the object. The floor must be flat otherwise values of d would be inaccurate and theoretical calculations would not be possible. Accurately measuring d must be addressed. If the value of d is purely observed by watching where the object lands, errors are bound to be made. If the object leaves a mark showing its first impact against the floor, the results will be more exact.
Distance between slide and floor
The distance h must remain the same throughout the whole experiment whatever the value of d. If the values of h varied it would be impossible to compare data obtained from the different methods and the theoretical predictions would not be possible to achieve.
Contact between object and slide
Contact between the object and slide should be a little as possible to reduce frictional forces between the two materials. The balance of weight must be equal over the surface of the object travelling down the slide. This will reduce any frictional forces present as one particular area will not slow the object more than another, thus equalising any frictional forces present. To have both minimal and equal contact between the top surfaces there must be more than one point of contact, but as few points of contact as possible. This leaves two areas of contact, the most practical shape for this would be a hollow cylindrical shape rested upon the edges of a rigid slide. The hollow cylinder would always have an equal weight upon the two edges of the slide (provided the edges are equal height), possible air resistance would be minimal due to small facing surface area. The depth of the cylinder would give a balanced pressure throughout the object. The ideal item to be used to travel down the slide is a metal ratchet socket. The ratchet socket must be larger than the distance between the raised edges of the slide, this means that there is a minimal sideways pressure on the side. The ratchet socket must be have a weight and shape that is equally spread throughout, avoiding unnecessary frictional forces and possible spinning motion. The slide must have minimal frictional resistance on the object, it must be smooth and have an equal shape throughout its length. There must be no dips, therefore the material must be ridged. The slide, as with the ratchet socket, will be made of metal with and have a smooth surface.
Contact between object and floor
In order for accurate results to be obtained in the experimental method there must be a pre-specified method of recording data from the first contact between the object and the floor surface. One option could be covering the ratchet socket with ink, and a mark left on a piece of paper. However, this would make a mess of all the equipment and stain carpet and clothes, as well as adding unnecessary frictional forces when on the slide. As paper is easy to perforate, there is no need to cover the ratchet socket in anything. The perforation could simply be observed and measured with a ruler. The paper and ruler have to be kept in the same position throughout the experiment. The ensure this, sellotape will be used to stick the ruler and paper to the floor. Sellotape will also be used to secure the slide to the table edge.