Centripetal Force

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SKH ST. MARY’S CHURCH

MOK HING YIU COLLEGE

AL Physics

Form 6S

Lab report

Centripetal Force

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 T provides both the centripetal force and a force to support the weight of the mass M. The tension T is given by T = mω2L, where ω is the angular speed of the mass.

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Procedure:

        1. The mass of the rubber bung, m was measured.

        2. One end of a 1.5 m length of nylon thread was attached to a rubber bung and the other end is attached through a glass tube, a paper marker and 2 slotted weights.

          3.        The position of the marker was adjusted so that it is about 1 cm near one end of the glass tube, and the length of the thread L from the    other end of the glass ...

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Here's what a star student thought of this essay

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.

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.

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.