Group3_6_ch5

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=Chapter 5: Circular Motion!= Lab Group: Magna, Lindsay, Katie

Centripetal Motion Lab
Date: 12/13/11

Task A: Magna Task B: Lindsay Task C: Katie Task D: Split up

__//Objectives://__ What is the relationship between Centripetal Force and mass, radius, and speed of a system?

__//Hypothesis://__ What is the relationship between speed and ∑Fc? As the Speed increases so does the forces, meaning it would be directly proportional.

What is the relationship between radius and ∑Fc? As the radius increases the force decreases, which would be inversely proportional. What is the relationship between system mass and ∑Fc? As the system mass increases so does the Force, they are directly proportional.

__//Materials://__ -Stoppers -String -Plastic tube -Tape -Hanging mass -Small mass rings

__//Procedure://__ First collect material, then take a two foot piece of the string and feed it through the straw and tie it around on one end the stopper and the weight on the other end. When the correct amount of weight is on either side conduct the first trial by holding the straw perpendicular to the ground with the mass closest to the ground. From their the mass needs to be spun at a constant velocity and radius. If the mass changes it's radius or velocity the string will move up or down. To help figure out if it is constant wrap a piece of tape around the string, under the straw where you want it to be through out the first trial. As the trials continue change the variable depending on what is being tested. __//Picture://__

__//Video://__ media type="file" key="Movie on 2011-12-13 at 13.29.mov" width="300" height="300"

__//Data And Graphs://__
 * Our Data**
 * Last Year's Data**



__//Sample Calculations://__

__//Analysis (Why we messed up)://__ We were changing too many variables at a time. For examples, we would change the centripetal force, the radius, and the speed all at once which obviously gave us poor results. We were so lost in our confusion that it took about 3 days to even realize what we had to do and at that point it was too late. So, with heavy hearts, we used the data from previous years so to have some hope of completing the lab and understand this particular law of physics.

__//Conclusion://__ We couldn't use our results from this lab, so we used the results Mrs. Burns gave us from previous years. However, we found some possible sources of error. For example, it was extremely difficult to measure the radius because we had to do it while the system mass was moving. This made it hard to see where it exactly hit the rule. We could have covered the ruler in marking paper. This way we could see exactly where it hit the ruler. It was very difficult to time everything because you weren't exactly sure when to start and stop timing. This became more difficult as velocity increased. Especially because we only had two people there on the day of this lab, it would have been more helpful to have more people time it. Lastly, more trials would have been a good addition to the data we received from past years.

**Activity: Minimum Speed at Top of a Circle**
Collect:
 * Mass (.05 kg)
 * 0.75 m String
 * Stop Watch
 * Meter Stick

Our Mass: 0.05 kg Class String Length: 0.75 m

Our Data:
 * = Trial ||= Time for 10 Period (s) ||= Time for 1 Period (s) ||
 * = 1 ||= 12.19 ||= 1.22 ||
 * = 2 ||= 12.26 ||= 1.23 ||
 * = 3 ||= 12.32 ||= 1.23 ||
 * = 4 ||= 12.50 ||= 1.25 ||
 * = 5 ||= 12.43 ||= 1.24 ||

Class Data:
 * Mass (g) || Velocity (m/s) ||
 * 6 || 3.98 ||
 * 10 || 3.7 ||
 * 20 || 4.5 ||
 * 50 || 3.82 ||
 * 100 || 3.92 ||

Theoretical Minimum Speed at Top of Circle: Our Velocity:

Our Tension at the Top of The Circle: Percent Error:

Possible Sources of Error and Conclusion: We may have measured the length of the radius incorrectly, or we could have changed where we held the string for each trial, which would have effectively changed the radius, which could negatively effect the results. Additionally, there were times that we swung the string too slowly and it bounced a bit at the top, which caused it to get a bit tangled. The calculations assume that there is zero tension, but in reality, there is at least a little tension when conducting this experiment, which explains why the percent error for the experiment is so high. Reflex time could also be a source of error; the person timing the circles may have stopped the timer too early or too late, which would also throw off the results slightly.

**Conical Pendulum Lab**
12/20/11 Task A:Katie Task B: Magna Task C: Lindsay Task D: Split up


 * Objective: What is the relationship between the period of a conical pendulum and its radius?**
 * Hypothesis:** The period and the radius of a conical pendulum are directly related.


 * __Sample Calculations:__**

Analysis:
 * 1) Calculate the theoretical period.
 * 2) Radius- 0.2 m = T- 3.26
 * 3) Radius- 0.5 m = T- 3.24
 * 4) Radius- 0.7 m = T- 3.21
 * 5) Radius- 1.0 m = T- 3.14
 * 6) Calculate the average experimental period for each radius.
 * 7) Radius- 0.2 m = T- 3.29 s
 * 8) Radius- 0.5 m = T- 3.28 s
 * 9) Radius- 0.7 m = T- 3.18 s
 * 10) Radius- 1.0 m = T- 3.07 s
 * 11) Discuss the accuracy and precision of your data.
 * 12) According to our percent error, we were pretty accurate. The highest percent error was when the radius was 1.0 m, 2.23%. This is probably because right before this trial, the string unstuck from the ceiling and it was rehung so this could have changed a lot. However, the rest of our experimental periods were extremely close to the theoretical periods. Our data was close to precise, as all our the times for the each trials at the same radius were close, such as 3.07 seconds and 3.08 seconds.
 * 13) Why didn’t we use the tangential axis at all in this lab?
 * 14) Because we were just using the horizontal circle the hanging pendulum made, we didn't need the tangential axis. Only gravity and tension of the string are influencing the horizontal circle.
 * 15) What effect would changing the mass have on the results?
 * 16) It would have no effect because the mass cancels out in the equation.
 * 17) How did period change as the radius increased? Is it a linear relationship? Why or why not?
 * 18) As the period got smaller, the radius increased. This is not a linear relationship because there isn't a direct or indirect relationship between the period and radius. They do both change but there isn't a set relationship.
 * 19) What are some sources of experimental error?
 * 20) The main source was measuring the radius. By having multiple trials, the average radius would give the best result. Also, the timing wasn't exact at all because it was just humans guessing when it made a full revolution and many people had different times. This would affect our experimental period. Also, as previously mentioned, the string fell and had to be fixed towards the end and we could see the difference in our percent errors.

Sample Percent Error Calculation: 

Moving in a Horizontal Circle Lab
1/3/12 Task A: Maggie Task B: Lindsay Marella Task C: Katie Task D: Split up


 * __Objective:__**
 * 1) What is the relationship between the radius and the maximum velocity with which a car make a turn?
 * 2) How does the presence of banking change the value of the radius at which maximum velocity is reached?
 * 3) How does changing the banking angle change the value of the radius at which maximum velocity is reached?

-If there is a bigger radius, there will be a bigger maximum velocity -This lets there be friction which keeps the car on the road and banking the turn makes sure the car stays on the road if it is going too fast -If there is a bigger angle, then there will be a smaller radius which means a smaller maximum speed
 * __Hypothesis:__**

We put a 5 gram mass on a rotational motion apparatus, which had a gate-timer positioned above it. We gradually applied increasing amounts of voltage to the apparatus which made it spin and slowly speed up until the weight flew off. Once the weight flew off we stopped the gate timer and used the time before, which was the time it took to move around the circle. We used this information to solve for the speed and were then able to find the max speed the table could spin before the weight flew off.
 * __Methods and Materials:__**

__**Data:**__

__**Graph:**__

__**Pictures:**__

__**Video:**__

__**Analysis:**__ Using the equation, find the coefficient of friction using the average period from the trials...see calculations below.

__**Sample Calculations:**__

__**Percent Error:**__




 * Find the percent difference between coefficient of friction from the equation off the line and your value. Discuss the difference between the 2 values.

There were a few errors that could be corrected if this experiment is done again. To start, we should have marked the exact spot we put the mass so that it would be in the exact spot each trial. Our rotational motion apparatus machine was having some difficulty staying at a constant speed, and sometimes it was just getting stuck or something, so this experiment should be done on a machine that works more constantly. Also, there is no way that Katie was able to stop the DataStudio photogate timer exactly when the mass began to fly off, so if there is a way that the timer stopped exactly on time that should be included in this experiment. In real life, this can be related to ice skaters when they are racing around in a circle. They want to go around the corners as fast as possible, but they want to do it so they don't go above maximum speed because then they would fall and possibly get hurt and lose the race. Because they want to win and not slip, it's important they stick to max speed so to not extend the radius.
 * __Conclusion:__**