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Centripetal Force

Extracts from this document...

Introduction

SKH ST. MARY’S CHURCH

MOK HING YIU COLLEGE

AL Physics

Form 6S

Lab report

Centripetal Force

Student Name

Li Yat Long (25)

Lab partners

Liu Tin Chun (26)

Chan Wai Kin (17)

Date: 31st October 2008

Title: Centripetal Force

Objective: To study the quantitative relationship between the centripetal force acting on an object and its angular speed.

Equipment: Rubber bung, Glass tube about 15 cm long, Slotted weights 20g X 20, 1.5m of Nylon thread, Paper marker, Metre rule, Stop watch, Triple beam balance

Theory: Centripetal force is the force acting towards the centre of the circle which makes a body move in a circular path. To keep a body moving in a circle of fixed radius, the centripetal force must change with the angular speed of the object. When a mass m attached to a thread is whirled around a horizontal circle of radius r, the tension

...read more.

Middle

5. The angular speed was kept constant so that the marker was always about 1 cm below the tube throughout. The time for 20 revolutions of the bung was measured by using a stop watch. One more confirmatory reading was taken and the mean time for 20 revolutions was obtained.

        6. The experiment was repeated several times, each time the number of slotted weights is increased by 2, until 10 slotted weights were on the line.

Independent variables: Mass of the slotted weights

Dependent variables: Time for 20 revolutions

Controlled variables: Mass of the rubber bung

          The mass of the slotted weights are controlled by increase the number of slotted weights by 2, that is increase the mass of slotted weight by 40g in each repeating experiment, until 10 slotted weights are on the line.

Results :

Mass of rubber bung (m) = __________ kg

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Conclusion

an="1" rowspan="1">

0.78

18.10

18.21

18.16

6.92

0.12

1.18

16.01

16.28

16.15

7.78

0.16

1.57

13.39

15.06

14.20

8.85

0.20

1.96

12.56

13.36

12.96

9.90

Data Analysis

centripetal force varies with the angular speed.

image01.png

From the graph, the centripetal force increase exponentially with the angular speed.

Conclusion

When the angular speed increases, the centripetal force increases. They are proportional.

Discussion

Source of error: the friction between the glass tube and the thread.

             Air resistance

             The force is not constant when the bung whirls.

To improve the accuracy of the experiment, lubricants should put on the glass tube’s surface that has contact with the thread. A constant force should be kept constant to make the angular speed be constant so that the marker was always about 1 cm below the tube throughout.

...read more.

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Here's what a star student thought of this essay

3 star(s)

Response to the question

The report, while not having an explicit question, addresses centripetal force very well. It is clearly laid out with clear sections and defines centripetal force at the beginning, something that many lab reports fail to do – define the thing ...

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Response to the question

The report, while not having an explicit question, addresses centripetal force very well. It is clearly laid out with clear sections and defines centripetal force at the beginning, something that many lab reports fail to do – define the thing that they are investigating. Most of this review will be in the level of analysis section due to this being more applicable for a lab report.

Level of analysis

In general the analysis in the report is satisfactory. The candidate addresses fundamental aspects such as errors well, however these should be elaborated on. He/she should talk more about how a certain error, such as friction between the thread and tube affected the results – both the magnitude and direction by which the error caused results to shift. Graphs are missing from the report, however this may be a problem with it being formatted on the website. Also, the candidate needs to be more precise. Saying “about 1cm” is bad in a lab report; they should say “1cm”. The word “about” suggests imprecision something that isn’t good in a lab report that will be marked. Linked to this they should say how many trials that they did rather than just “several trials”. The conclusion should be elaborated on – give an equation for the centripetal force to the angular speed, stating a coefficient if the values are directly proportional.

Quality of writing

Quality of writing is good, however there are some spelling and grammar errors, such as “increase” instead of “increases”. Again, sections are clearly broken up through the use of headings and terms are well defined. Overall the report is good, however there are some flaws, such as too little said about errors that should be fixed.


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Reviewed by davo11 29/02/2012

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