In this investigation, it is vital to be able to accurately determine the dimensions of an object (particularly its radius), an objects mass, the distance the object is traveling, the angle at which the object is traveling down, and the time it takes for the object to get from the start line to the end were not able to be accurately determined. To limit the amount of inaccuracy, an electronic balance was used to as best determine an objects mass.Venire calipers were implemented to determine the diameter of all the objects instead of using a 30cm ruler. To determine accurately the angle of elevation, instead of using a compass, basic trigonometry was used by measuring two lengths. Also a level surface was used to make sure this angle was accurate.
To determine the time taken for the object to reach the end of the incline, two timers were given stopwatches.Although for further experimentation, a motion sensor can be used to more accurately determine the time, and also to plot displacement/time graphs which will be helpful in accurately confirming the conservation of energy of a rolling object. In this investigation, because of time constraints, stopwatches seemed to be the much better option. To reduce their error each object was raced numerous times and the same two timers were used every time.Another source for the error in this experiment is retarded forces which were deemed to be negligible. As an object rolls own the incline, there will be air resistance slowing its motion.
However, this will not have a significant effect, and is not necessary to control in further investigations. To avoid experimenting near other people, the investigation was performed outdoors. This exposes the objects, particularly the lighter ones, to the effects of wind gusts. In the future, this experiment should be commenced indoors to limit this error.
Many of the calculations in this experiment were dependent upon the assumption that the objects will be rolling down the incline only, with no slip occurring (its point of contact with the incline has zero velocity). Towards the end of the calculations (Table 40) this assumption was found to actually be fact, since we were operating at angles that did not allow slip to occur. However, depending on how the object was released always could determine if it no additional velocity was given to it.
In the preliminary testing the object was released by moving the ruler upwards. This was changed to releasing the objects my moving the ruler forwards quickly to prevent giving the object additional velocity. The ruler was also help parallel to the end of the board (marked by a line) so that the object will be released straight. If the object goes down at an angle, it is traveling a further distance, which results in inaccuracies. Releasing the object straight prevented this from occurring, and if the object was noticed to be going down at an angle the times were disregarded.CONCLUSIONThe results of this investigation supported the equation by indicating that the final velocity of the object is independent on its mass, radii and length. The objects shape and the height at which it was released were found to have an effect on its final velocity.
It was postulated that water inside a can as it rolls down the incline, does not roll with the can, but slides, reducing the objects rotational inertia. The moments of inertia of the objects were able to be determined and were found to be within 10% accuracy of the theoretical values. The conservation of energy was also found to comply with a rolling object down an incline. However, throughout the course of this investigation, certain errors in the design of the experiment and the procedure would have had an effect upon the accuracy of the results.PART II – DESIGN OF THE SKATEBOARD WHEEL ABSTRACTThe following design relates to wheels of the type used to rollingly support a skateboard or similar conveyance upon a surface. More particularly, the subsequent design relates to wheels which include a circumferential trough therein for enhanced wheel performance.
Skateboarding has established itself as a sport of exceptional popularity. While skateboards have been provided with various different configurations, most common standard skateboards include a generally flat board supported upon wheels.Most typically, forward and rearward trucks are attached to an underside of the board with a pair of wheels rotatably supported by each of the trucks. The trucks typically have a form if resilient coupler which allows the board to pivot relative to a plane in which the two wheels supported by the truck are supported. Hence, the board can be angled away from horizontal somewhat while keeping all of the four wheels rolling upon the ground. Such angling of the board also turns the wheels for directional control of the skateboard.
The wheels provided with the skateboard can have different configurations, and can be formed from different materials. However, most commonly skateboard wheels are made of made of a solid urethane material with a generally cylindrical form. This cylindrical form is defined by an inner side surface and a outer side surface which are generally circular and a tread surface between which is generally cylindrical as well. A central axis of the wheel typically has a hollow bore passing through which allows the wheels to be mounted to an axle supported by the truck. The wheels can either rotate upon the axle, generally acting in the form of a journal bearing, or can have a roller bearing fitted within the wheel with an inner race coupled to the axle and an outer race coupled to the wheel races rolling relative to each other.Most typically the urethane from which the wheels are formed has hardness on the durometer from 75 to 103.
Diameters for most skateboard wheels generally vary between about 50 millimeters and 77 millimeters. The softer urethanes generally provide greater traction and are most suitable where maneuverability is at a premium. Urethane wheels having a greater hardness are generally more desirable where greater speed is desired the harder wheels also have longer endurance. Typical skateboard wheels have a width of generally between 30 to 40 millimeters.
Also, skateboard wheels vary somewhat in the degree of roundness or abruptness that the tread surface transitions into the outer side surface and inner side surface of the wheel.Skateboard wheels, while varying slightly, have thus become rather standardised with the only variables being slight variations in diameter, urethane hardness and abruptness of the inside and outside edges of the tread surface. Accordingly, a need exists for skateboard wheels which depart more radically from standard skateboard wheel configurations, to provide a superior ride, the potential for greater speed, greater mobility and responsiveness in turning, with less friction provided by the wheels so that the overall ride smoothness is enhanced.