Clock+Lab

=Clock Design: Simple Harmonic Motion= Date of Publication (Date of Most Recent Edits)


 * Participants**: Megan Fucci, Niko Pearson, Kristin Kozlowski
 * Purpose**: The purpose of this lab is to design and characterize a clock that is makes accurate time measurements in the range of 30 to 90s.
 * Lab Documents**: [[file:Simple Harmonic Motion.doc]]


 * Brief Description Clock Design**: Our clock was a single spring attached to a rod by a string. Its total length is 23 and 9/10ths cm. The rod is held up by two poles connected to the table. The clock can perform fairly accurately for at least 90 seconds. You can do this by attaching 720grams to the spring and pulling it down to 59 and 2/10ths cm. This allows the spring to bounce at about 1 second per bounce. The standard error would give or take a second away from the time counted. To measure the time you will need some sort of timer, or stop watch. First, you will pull the spring to 59 and 2/10ths cm and start the timer right when you let go of the spring. You then count how many bounce you want to measure (30,60,90) and stop the clock when you count enough bounces. The number of bounces and time measured should be close. For example, one of our tests had 30bounces in 29.39seconds. If it's more than 10% off you should check your weights and measurements and try again.

Provide a short (one paragraph) description of the clock designed. Also provide a clear, very detailed instructions for operating the clock including how to start the clock and how to measure a time using the clock. Supplement this description with images, video, etc. to make clear and interesting.


 * Specifications of Clock:** With a coil and string at a total length of 23.9 cm. and a mass of 720g, our clock was very accurate. As long as the spring was pulled to exactly 59.2 cm. each time, our accuracy was less than 0.02 bounces per minute off. When we tested our clock for exactly 30 bounces, it took 29.42 seconds which is equivelent to a speed of 1.019 bounces per minute. When we tested our clock for exactly 60 bounces, it took 59.54 seconds which is equivelent to 1.007 bounces per minute. Lastly, when we tested our clock for exactly 90 bounces, it took exactlyt 88.93 seconds which is equivelent to a time of 1.012 bounces per minuite.

Provide data that describe the accuracy of the clock for measureing times between 30 and 90s. A graph may be useful. Be sure to describe how the tests were performed (procedure). speed = distance / time || Average Bounces Per Second X = Mass Y = Bounces Per Second > **Conclusion**: > Our experiment did produce a valid result. We were accurate within 2% of the stop watch. The times and masses were also tested multiple times reducing the probability for human errors, such as bad measurements or miscounting. We made appropriate measurements of our strings, springs and variable like how far we pulled down the spring. We recorded all the masses we used. All of this makes our experiment reproducible. The experiment could be improved if there was someway to create a latch, that the spring could hook on to at 59 and 2/10ths cm. The latch could be triggered by the timer, so the timer and the spring bouncing start at the exact same time. That eliminates some of the human error involved in the experiment, allowing you to get more accurate measurements of times and bounces.
 * Sample Calculations:** Describe or reproduce any calculations that are performed during the experiment (other than averaging). For example, if you use a distance and a time to calculate a speed, you should show:
 * //Speed calculation// || The speed in meters per second was calculated by taking the measured distance in meters and dividing by the time elapsed in seconds.
 * Design Variables:** Provide a brief discussion of which variables you think may influence the operation of your clock and how you predicted (pre-lab) that these would influence the performance of your clock.
 * Studied Design Variable 1:** Weight of the mass- Increasing the wight of the mass at the bottom of the spring slows the bouncing and decreases the frequency.
 * Studied Design Variable 2:** Distance Pulled (from the top)- The further the spring is pulled down, the shorter the frequency. If you were to pull the spring down 1cm as opposed to 10cm, the spring would bounce more times per second because of the smaller recoil distance.
 * Studied Design Variable 3:** Length of the Spring- If the spring is short, the frequency will increase because the distance of the bounce is shorter. If the spring is long, the frequency will decrease because the distance of the bounce is longer.
 * Studied Design Variable 4:** Length of the String- The longer the string is, the more slack there is to allow to swing and bounce from side to side. This decreases frequency to a point below the desired 1 bounce/second and throws of the accuracy of the clock
 * Lab Questions**: Write out and answer any questions that are included as a part of the lab.
 * 1) Describe in detail how your device may be used to measure an event that lasts 60s. What would the accuracy of this measurement be? To measure a 60second event you will need to pull the spring down 59 and 2/10ths cm and let go of it when you want to start timing it. You, or someone will have to count the number of bounces once it bounces 60 times you've reached you time limits. The accuracy will be within about one second.
 * 2) Which variable that you studied had the most significant effect on the frequency/period of the clock? If you built your clock with a 20% increase in this variable, what would the new frequency/period of the clock be? Support your answer by referring to data in your report. As we changed the mass that huhng off the end of the spring, the frequency of the clock visibly changed; this would be the most significant variable. The more mass added, the slower the frequency. Due to the added weight, the coil took a longer period of time to reach it's destination; this is greatly connected with gravity's affect on mass. A 20% increase in mass would add 144g to the weight making the total weight 864g compared with the original 720g. This would significantly slow down the frequency of the clock. For example, changing the mass of our clock from 550g to 700g decreased the frequency by 0.105 bounces per minute.
 * 3) The length of the string was the variable in our design that had the least significant effect on the frequency of the clock. A 20% increase would bring the string from about 5cm to 6cm. The increase would give more slack between the spring and the support bar, causing the string to swing even more so than normal ("normal" not being very much)from side to side, instead of remaing still to allow the spring to bounce straight up and down. This would result in a decrease in frequency.
 * 4) Our clock design would not be accurate in measuring extened lengths of time (between 10 and 15 minutes), and that is because the spring in our design loses energy as it bounces and would soon come to a stop if we let it bounce for too long. However, if the support bar that the spring is tied to could oscillate up and down, energy would be put back into the system and sustain a decent frequency for extended time periods.
 * A statement about whether you think that the experiment produced a valid and reproducible result and reasoning supporting your statement.
 * A suggestion as to why your experimental results differ from any accepted value or your expected result (if appropriate).
 * A suggestion for a simple improvement to the experiment. Think about what caused problems, measurement inaccuracies, or inappropriate simplifying assumptions and propose a change. A sketch may be helpful.

> > //Don't forget to link to your lab report from the lab reports page and to include a link to your lab report in your reflection.//
 * Independent reflection:** One lab report will be turned in for each group. In addition, each student must complete //independently// a reflection addressing the following questions:
 * How was the process of designing and testing a clock similar to the scientific method as discussed in class?
 * How did it differ?
 * What "steps" in the scientific process were present and which were missing?
 * Was there a part of the activity that is not a part of the scientfic process?