Nyeongminlee

Conclusions

 

Patterns and Trends

 

Journey of Marine Park-Island center and Island center-Island kitaguchi have similar pattern of graph. In both graphs, velocity increases until the maximum velocity as time goes, stay a while on the maximum velocity, and velocity decreases until 0 m/s. Although they have similar pattern, there is a difference. Marine Park-Island center part takes longer time to reach to the maximum velocity and also from the maximum velocity to 0 again. On the other hand, Island center-Island kitaguchi gets to the maximum velocity faster than Marine Park-Island center and also takes less time to change from maximum velocity to 0m/s. Also, maximum velocity of Island center-Island kitaguchi is higher than Marine Park-Island center. Because of these reasons, graph of Island center-Island kitaguchi is steeper, or narrower, than Marine Park-Island center part.

 

 

Reliability

 

The data were quite consistent. There was 3 trials of this lab. When I compare data of three trials, data is close to each other. For example, average velocity of each part is almost same, only 0.1m/s difference between data. The biggest difference between trials is taken time to accelerate from rest to maximum velocity of Island center-Island kitaguchi, which was 2.9 seconds. The average difference between data of each trials is about 1.5 to 2. I think it is consistent enough.

 

There were enough repeats to give a reliable set of data. Our team got three repeats of data. All three trials have quite closed data to each other (which was quite consistent), which means set of data is reliable.

 

Effect of uncertainty/ precision

 

1. Distance

We only got the distance by map using scale. Therefore, it has quite high uncertainty. Also, we treated this journey as moving straightly, so there must be some gap between the actual and calculated displacement.

2. Time

We used stopwatch with uncertainty of 0.1 second, which is very accurate. However, we timed with our eyes and hands, which is not accurate enough. Because of that, even if the material had accuracy, our accuracy is weaken. It will affect the data of time, and also all other data which was calculated based on the data of time.

 

Qualitative Data

On the train, I could figure out that train speeds up very fast and maintain that speed for some time.

journey from Marine Park to Island Center took more time than from Island Center to Island Kitaguchi.

Maximum velocity from Island Center to Island Kitaguchi was higher than MP-IC.

 

 

 

Validity of the Hypothesis

 

Component	Value & unit		Component	Value & unit
Total Journey Time(s)	Predicted: 176 Measured: 176.6		Max. velocity MP-IC(m/s)	Predicted: 12.5 Measured: 13.0
Average velocity (MP-IK)(m/s)	Predicted: 5.8 Measured: 5.78		Time taken to accelerate from rest to max velocity, MP-IC(s)	Predicted: 26 Measured: 33.0
Time MP-IC(s)	Predicted: 68 Measured: 68.8		Average acceleration from rest to max velocity, MP-IC(m/s/s)	Predicted: 0.48 Measured: 0.39
Average velocity (MP-IC)(m/s)	Predicted: 8.2 Measured: 8.1		Max. velocity IC-IK(m/s)	Predicted: 14.7 Measured: 14.4
Rest time at IC(s)	Predicted: 58 Measured: 57.8		Time taken to accelerate from rest to max velocity, IC-IK(s)	Predicted: 20 Measured: 18.8
Time IC-IK(s)	Predicted: 50 Measured: 50.0		Average acceleration from rest to max velocity, IC-IK(m/s/s)	Predicted: 0.74 Measured: 0.72
Average velocity (IC-IK)(m/s)	Predicted: 9.1 Measured: 9.1

 

General comment

 

Most of predictions agreed with the measured outcomes.

Most of data has difference of ±0.1. For example, predicted and measured data of Time IC-IK and Average velocity of IC-IK are exactly same and average acceleration from rest to maximum velocity in IC-IK has only difference of 0.02.

However, there are some datas that had more gaps between predicted and measured data. For example, time taken to accelerate from rest to maximum velocity in MP-IC has difference of 7.

 

Conclusion and Explanation

 

-Constant motion in the velocity-time graphs

In any velocity of motion, when the velocity is constant, it is straight, horizontal graph. When the velocity is constantly 0m/s, or the object is stopped, the graph will be same as x axis. When the velocity is not 0m/s, such as 12m/s, it will also draw a horizontal graph at 12 of y axis (velocity).

 

-similarities and differences between the MP-IC and IC-IK parts of the velocity-time graph

General shapes are same each other for MP-IC and IC-IK. The velocity increases until the maximum velocity, stay on the maximum velocity and decreases until 0m/s. However, the gradient of increasing and decreasing in velocity is different. IC-IK part takes much less time to get to its maximum velocity than MP-IC.

 

-What assumptions have we made in this investigation and how might they have affected the results?

We assumed that IC-IK will take less time to reach higher maximum velocity and take less time to get to 0m/s again than MP-IC, which have been proven by this investigation. Because of this, we also assumed that acceleration of IC-IK will be much higher than MP-IC, which also have been proven. Because the assumption and proven results are similar, there is very less gap between predicted and measured data.

 

Evaluation

 

 -reliability of the method:

I think this wasn’t very reliable.

Because

1. We timed in hand.

This can give the general pattern of the train movement, but not accurate data of specific time at certain point. Even though we had three trials, our hand can’t time differently in 0.1 seconds. We should’ve used other methods to get more accurate data of time.

2. Data only based on the time.

All of our data is based on the data of time. The very first raw data I got is time. Time of whole journey, time between stations and time per each tracks. The time is not accurately recorded. Then, it also means our velocity which is calculated with the data of time is not also accurate and so is acceleration.

 

-Comment on the validity of the method.

The method described the motion of the Rokko Liner well. By the time taking to parts to parts, we got the time, and from the data of time, we calculated velocity and acceleration. It is enough to describe the motion of the Rokko Liner quantitatively. I think we got enough data, which was three repeats because repeats were consistent which was enough to describe Rokko Liner’s motion clearly. I think when I measured the velocity by more accurate method, such as using app or machine that can check the velocity of a moment, then it will give us clearer data of the motion of Rokko Liner.

 

 

Solution to problems in the method

 

Source of error/limitation	Impact on results	Possible solution
timing-stopwatch as very high accuracy, but hand timing has high uncertainty	It will not give accurate data of time which can change the other data, such as velocity and acceleration.	Take a video of track with the stopwatch going on the bottom of the angle so that we can play the video slowly and check the time at certain point. For example, if we want to check when the train passes the first and second track, we can play the video in slow motion at that point, and see the stopwatch underneath the video so that we can get comparatively accurate data.
maximum velocity-because we calculated it by the time that train passes each tracks which is 25m apart from each other, it is not very accurate way to find the velocity.	Maximum velocity might not be accurate. Then, acceleration also cannot be accurate enough.	On the bottom of the video, also put the velocity checker next to the stopwatch such as the app on smart phone. It will give us more accurate data of velocity. We can replay the video and the highest number that velocity checker shows will be our maximum velocity.
Displacement-we only calculated the displacement using scale on the map which might be different with the actual data.	It doesn’t only change the data of ‘displacement’ but also the velocity of MP-IC, IC-IK and total which are calculated using displacement.	First solution is to make the scale smaller on Google Map. It will give more accurate displacement than bigger scale. But it is not also the real data, so there must be some error. The best way is to really ‘measure’ but it is impossible because we can’t measure the straight line from MP station to IK because of buildings, roads, and other land shape between two stations.

-Suggestions for further investigation

 

1. We can investigate about the whole movement of Rokko Liner.

From Marine Park to Sumiyoshi, from both sides. Also, we can compare the difference between journey from Marine Park to Sumiyoshi and from Sumiyoshi to Marine Park.

 

2. Not only for Rokko Liner, but also all the other moving things.

We can do the same investigation on the bicycle, car, or any other moving things. For example, for the car, there is a speedometer which will help investigating, like finding the maximum velocity. (we don't have to calculate, but just read it)