1027 words - 4 pages

INVESTIGATING CIRCULAR MOTION 11/3/04AIMTo examine some of the factors affecting the motion of an object undergoing uniform circular motion, and then to determine the quantitative relationship between the variables of force, velocity and radius.APPARATUSRubber bung Metre rule 50 gram slot massesGlass tube 50-gram mass carrier 50-gram slot masses Metre ruleStopwatch Sticky tape Metre rule StringTHEORYAs in Jacaranda HSC Science Physics 2 p.54In this experiment when the rubber bung is moving in a circular motion and the string it is tied to moves neither up or down a constant radius is being maintained. For this to be true the centripetal force must equal the gravitational force henceMv"/r = mg from thisv"/r =mg/M and v" ∞ r therefore as v increases so does r and vice versa.Wherem = Mass of mass carrier + masses (kg)g = acceleration due to gravity 9.8 m/sec"M = mass of object in motion (kg)v = instantaneous velocity of mass (m/sec)r = radius of circular motion (m)METHODAs in Jacaranda HSC Science Physics 2 p.54However instead of measuring the time for 10 revolutions, the time for 20 revolutions was measured, this allowed more accurate results to be obtained. Furthermore the lengths given in the book were used as merely guidelines and not followed precisely also 50 and 100-gram masses were used.RESULTSForce (N) Radius(m) Period (20 Revolutions) (s) Orbital Velocity v m/s v"g x 50g 1.03 19.47 6.65 44.19g x 50g 0.83 17.02 6.12 37.55g x 50g 0.64 14.14 5.68 32.35g x 50g 0.37 9.94 5.2 27.04g x 100g 1.06 16.86 7.9 62.41g x 100g 0.82 14.4 7.15 48.702g x 100g 0.62 12.8 6.08 37.01g x 100g 0.44 10.2 5.42 29.38Results of circular motion experimentVelocity" versus rBy plotting the graphs it can be observed the y axis is equal to v" and the x axis is given as r (radius), the gradient is given by (y2 - y1) / (x2 - x1). By working out the gradients it can be seen that the gradient for 50-gram masses is approximately 26, whilst the gradient for the 100-gram graph is approximately 53.27, approximately double the gradient of the 50-gram graph. It can also be observed the any two points taken for the 50 gram graph will have a relatively close gradient to any other two points, hence the graph has an almost constant gradient. The significance of all this will be discussed in the questions.QUESTIONS1 What is the relationship that these graphs indicate?The graphs show that v"is proportional to radius as straight lines with constant gradients were achieved when drawing the graphs of v"/r (as explained before). This phenomenon is a result of the gradient being equal to mg/M, as v" = r mg/M, in our experiment all these mass factors were controlled and kept constant ie 18.49 gram bung was used and 50 or 100 gram mass was used as needed, also gravity was constant so mg/M was constant and so was the gradient. Hence mg/M is a constant and v (orbital velocity) is directly proportional to r (radius of orbit).Furthermore when the graphs were drawn it was seen that when that...

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