PIRATE SHIP EXAMPLE REPORT WRITE UP

Transcription

1 PIRATE SHIP EXAMPE REPORT WRITE UP Title Aim period Pirate Ship investiation To find the relationship between the lenth of a pendulum and its Independent variable the lenth of the pendulum. I will use lenths of 0.00, 0.400, 0.600, 0.800, and 1.00m. Dependent variable the period of the pendulum (the time to swin from one side to the other and back aain) (MUST HAVE Independent and dependent variable for Achieved) Control variables (MUST HAVE for Merit/Excellence) 1. I will measure the lenth of the pendulum the same way: from the bottom of the cork that the strin is threaded throuh, to the centre of mass of the pendulum bob.. Use the same ruler all measurements. 3. Release the pendulum from the same anle each time (approximately 15 ) 4. Release the pendulum so that the it swins perpendicular to the slit in the cork that is holdin the strin. Accuracy improvement (MUST HAVE for Merit/Excellence) 1. I will time 10 oscillations and divide by 10 to et the time for one period. This will reduce the effect of random variations in my times.. I will repeat the timin measurement for each lenth 5 times and take the averae. 3. I will reduce parallax error when measurin lenth by makin sure I am viewin the scale at 90, and makin sure the ruler is close to the strins. Method 1. Set up the equipment as shown in the diaram.. Adjust the lenth of the strin to 0.00m 3. Hold the pendulum bob to the side, deflectin it by around 15 and let o 4. Time 10 oscillations and record the time 5. Repeat step 5 until 5 times are recorded. 6. Repeat steps to 6 for lenths of 0.400, 0.600, 0.800, and 1.00m. 7. Process results to enable a relationship to be worked out. C lam p Clamp R uler B ench enth Retort stand Heavy mass to prevent the wood frommovin Bench Mass

2 Results enth of strin, (m) for (m) Must have at least one for Achieved Averae for 10T (s) Rane for 10T (s) Must have T and error bars for Merit/Excellence for 10T Time for one period T (s) for T (s) Times for 10T (s) 0.00 ± ± ± ± ± ± Processin The unprocessed data above would not ive a straiht line raph. As T π T is proportional to, therefore I will need to raph T aainst to et a straiht line raph and work out the equation. enth of strins, (m) for (m) % Unc Abs Unc % Unc 0.00 ± % % ± % % ± % % ± % % ± % % ± % % % and processin optional for Merit/Excellence (as lon as you have correct Time and error bars on your raph) Graph on the next pae The absolute values for are too small to plot on the scale that I have used on my raph Gradient of best fit line (MUST HAVE for Achieved) Rise.5s Run 1.14 m Gradient.5/ (s/ m) Gradient of error line (MUST HAVE for Merit/Excellence) Rise.5s Run 1.06 m Gradient.5/ (s/ m) Difference between radient of best and error line Δradient (1sf) Gradient with.0 ±0.1 (s/ m) (MUST HAVE for Merit/Excellence)

3 Period (s) Period v square root of lenth.50 Error line MUST HAVE for Achieved.00 Error bars on each data point MUST HAVE for Merit/Excellence (can use larest Time for all Time error bars) Best fit line MUST HAVE for Achieved Square root lenth ( m) 3

4 Conclusion - For achieved level The relationship is stated and reconition that the experimental relationship is consistent with the theoretical relationship. In conclusion the period of the pendulum is related to the lenth of the pendulum by T.0 COMPARING, Method 1 Comparin my equation T.0 to the iven equation T π I can see that my radient value,.0, should be equal to π π and.01, which shows that my relationship is consistent with the theory. 9.8 COMPARING, Method Comparin my equation T.0 to the iven equation T π I can see that my radient value,.0, should be equal to π. Rearranin π.0 ives π , which shows that my relationship is consistent with the theory as my value for of 9.87 is close to the theory of

5 Conclusion - For Merit and Excellence level The relationship is stated and an appropriate comparison is made between the theoretical value of the radient and the equivalent experimental value. (Accept a comparison between a constant calculated from the radient and a theoretical value.) The comparison includes a consideration of uncertainties. In conclusion the period of the pendulum is related to the lenth of the pendulum by T (.0 ±0.1) The in the radient is due to the uncertainties that I accounted for durin the experiment and processin of the data. COMPARING, Method 1 Comparin my equation T (.0 ±0.1) to the iven equation T π I can see that my radient value,.0 ±0.1, is equal to π π π and This shows that althouh the value of my best fit line,.0, is slihtly lower than the theoretical value for the radient of.01, it is well within my rane of values for the radient which is 1.9 to.1. My values are between (1.9/.01)x10095% and (.1/.01)x100104% of the theoretical value. COMPARING, Method Comparin my equation T (.0 ±0.1) to the iven equation T π I can see that my radient value,.0 ±0.1, is equal to π So π.0 π Maximum value of radient.1 So π.1 π So Minimum value of radient 1.9 π 1.9 π This shows that althouh the value of iven by my best fit line, 9.87, is hiher than the theoretical value of 9.81, it is well within my rane of values which is 8.95 to My values are between (8.95/9.8)x10091% and (10.94/9.8)x10011% of the theoretical value. 5

6 Discussion For Excellence - markin schedule: The discussion shows evidence that the student has sufficient depth of understandin of the experimental process to be able address critical issues such as: 1. other variable(s) that could have chaned and sinificantly affected the results, and how they could have chaned the results. (Note that it is not enouh to just state the results would be inaccurate.). the limitations to the theory s applicability both in the practical situation and/or at extreme values of the independent variable. 3. any unexpected outcomes of the processin of the results and a suestion of how they could have been caused and the effect they had on the validity of the conclusion. (Note that the aspects discussed should not be what would normally be considered as mistakes in experimental procedure such as failin to fix a wobbly retort stand - nor should they relate to just standard experimental procedure.) The evidence may be shown in two statements that show ood understandin or at least three (dependin on the depth of the understandin shown) statements that each show some understandin. The discussion points should be well reasoned and include clear and loical links between what has happened and the effect it has had on the results/conclusion. SEE NEXT PAGE FOR EXAMPES T If the line is too steep then is too small <9.81 ine with radient that ives 9.81 If the line is too shallow then is too bi >9.81 6

7 Discussion - examples 1. Control variables that could have affected my experiment One of my control variables was makin sure that I always measured the lenth to the same position on the pendulum bob (i.e. to the centre of mass). If I did not do this, for example if I measured to the top of the pendulum bob, the actual lenth of the pendulum would have been loner than what I measured and the time periods would have been loner. EXTRA: This would affect the radient of my raph by makin it steeper than it should have been. As the radient is equal to π/ this would have iven a value of smaller than 9.81 ms -. a. imitations of the model compared to real life The formula would not apply in real life as the suspensions would be two steel beams, not strin. Because the steel beams have more mass, this would affect the position of the centre of mass, makin it much hiher up than my model. This would make the effective lenth in the real life situation shorter than the lenth to the ships centre of mass, makin its period shorter. b. imitations of the minimum and maximum values of the independent variable The minimum value for which this relationship will apply is limited by the size of the pendulum bob. The fishin sinker that I used is approximately 3.5cm lon, includin the eyelet used to attach the strin, so the pendulum lenth could not be adjusted to lenths shorter than that. 3. Unexpected outcomes of the processin/results (i.e. reasons why your radient / value for could be different to the theory, but NOT mistakes) As the mass swun back and forth it also spun. The spinnin caused the strin to untwist, increasin the lenth of. The increased lenth would cause the time period to be reater, increasin the value of the intercept. I intended to use parallax error reduction, but found it difficult to hold the ruler in place when measurin the loner lenths and ended up lookin down at the scale from above, leadin to the lenth of the pendulum bein loner than intended. This would have made the loner lenths too lon, and iven periods that were too lon. EXTRA: This would affect the radient of my raph by makin it steeper than it should have been. As the radient is equal to π/ this would have iven a value of smaller than 9.81 ms -. When I adjusted the lenth of the pendulum I wound it around the clamp. I noticed that for part of the swin the strin was loner as it swun away from the clamp and shorter when the strin was up aainst the clamp. As I measured from the top of the clamp this would have made the lenths too short for part of the swin and iven times that were shorter than they should have been. EXTRA: This would affect the radient of my raph by makin it shallower than it should have been. As the radient is equal to π/ this would have iven a value of reater than 9.81 ms -. WEAK EXCEENCE With my raph there is an intercept at T -0. s, implyin that the period is neative, which cannot happen. A possible reason for this is the way I timed the pendulum. I juded the end of the 10 oscillations by eye, but if I anticipated the end point too early, my times would be too short, and the periods would be shorter than they should be, causin the neative intercept. CANNOT INCUDE MISTAKES IN THIS SECTION - e.. I accidentally timed 9 oscillations instead of 10, or I accidentally measured 99cm instead of 100cm. 7