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Determination of the acceleration due to gravity (g)

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Introduction

Determination of the acceleration due to gravity (g) By-nanding Li Introduction Gravity is the force at which the earth attracts objects towards it; also know as the weight of objects. When objects fall towards the earth, their acceleration increases because of the gravity. This acceleration due to gravity is dependent on the object's mass. A free falling object, if gravity s the only force acting on an object, then we can know the object will accelerate at a rate of 9.81ms-2 down toward the centre of the earth, this is known as acceleration due to gravity and is given the symbol 'g'. We can find the force causing this acceleration using: F = ma And weight for the object: G = mg Where the 'm' is the mass of object and 'g' is the acceleration due to gravity. However, acceleration due to gravity is not the same through out the universe. The moon has a smaller acceleration due to gravity than the earth. If we were to drop a stone on the moon, it would fall more slowly. This does not mean the mass of the stone is changed from the earth to the moon, this means the moon has less attraction to the stone and the acceleration due to gravity on the moon is about on-sixth of that on the earth: g moon = 1.6 ms-2 In ...read more.

Middle

= acceleration / acceleration due to gravity 'g' t = time travelled for free fall ball because: u = 0 ms-2 therefore: h = 1/2 gt2 so : g = 2h/ t2 where: g = acceleration due to gravity(ms-2 ) h = the distance for the ball travelling from the rest to the receptor pad( m ) t = time taken to fall( s ) From this equation, we can see the 'g' can be determined by measuring the time( t) and the height( h ). Therefore we can determine the g by simply dropping the steel ball from a measured height and measuring the time it is taken to reach the pad. After this, I plotted a graph with height against time2 and rearranged the formula to find out the gradient of the line. In order to find out the gradient, I drew the line of best fit which nearly goes through all the points on the graph. The line of best fit shows a positive correlation which shows that the height is directly proportional to the time2 . i.e. if the height was doubled, the time would be doubled. Therefore, the gradient of the line which is the acceleration due to gravity can be calculated by using the formula: g = 2?h/ ?t2 ?h = 0.32m - 0.17m = 0.15m ?t2 = 0.068s2 - 0.036 s2= 0.032 ...read more.

Conclusion

That is means there is a big error in this experiment. The experiment itself is flawed, as friction on the tape passing through the timer, and air resistance would both decrease the acceleration of the tape. Therefore this would result in a lower value for g . Another method is done by suing a light gate. In this case, this method gave me the most accurate value : g = 9.82 ms-2 , because this value is calculate from the computer and this is the easiest way to get the value of g . However this method may give random errors, as there is no way of regulating the angle or tilt that the card is at when it passes through the light beam. This has an effect on the reading given, as the length of the card interrupt will change due to this tilt. The tilt of the card could increase the g value also means that this experiment may produce unreliable and inaccurate results. Consequently, I think the best way to determine g is by suing an electronic time. Overall, I think my experiment went quite well and the results I got for g is reliable and accurate. If I had more time, I would like to increase the height of which ball fell, I think this would give me a more accurate value of g. Ideally, I think it would be interesting to see how g change in different location. ...read more.

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Response to the question

There are several misconceptions and lack of precision with physical ideas in the work. Notably, not mentioning that all bodies with mass are affected by gravity, that mass is independent of acceleration, when neglecting air resistance, and thinking that air ...

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Response to the question

There are several misconceptions and lack of precision with physical ideas in the work. Notably, not mentioning that all bodies with mass are affected by gravity, that mass is independent of acceleration, when neglecting air resistance, and thinking that air resistance is less inside.
Generally, a lot of planning has gone into this experiment. It has been clearly structured but the length of the report made it difficult to follow as it was explaining three separate experiments.

Level of analysis

The way this experiment was carried out appears good though diagrams would aid the reader's understanding. The use of uncertainties is good and well explained. However it is very important that the graph is shown as this gives a good indication of how close the points are to a line of best fit.

Quality of writing

The writing is generally good but has some typos. Most scientific terms are spelt correctly.


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Reviewed by k9markiii 05/03/2012

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