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Determination of the acceleration due to gravity (g)

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Determination of the acceleration due to gravity (g)

By—nanding Li


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

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0.19+/- 0.01

0.036+/- 0.02





0.21+/- 0.01

0.044+/- 0.02





0.23+/- 0.01

0.053+/- 0.02





0.26+/- 0.01

0.068+/- 0.02





0.28+/- 0.01

0.078+/- 0.02





0.30+/- 0.01

0.090+/- 0.02





0.32+/- 0.01

0.102+/- 0.02





0.34+/- 0.01

0.116+/- 0.02





0.35+/- 0.01

0.123+/- 0.02





0.36+/- 0.01

0.130+/- 0.02


In this experiment, I carried out 12 different height in the range of 0.1m to 0.7m for the free fall experiment. I took three reading for each height and took an average for each the times. Then I divided these values by 3 to get the average reading for the time.

Average = t1 + t2 + t3 / 3

This would influence the accuracy of my results.

To calculate the acceleration due to gravity ‘g’ is acquired by measuring the time and height through a free fall ball and use following equation:

                                               S = ut + 1/2 at2

S = height( h ) / displacement

U = initial velocity of free fall ball

       In this case, u = 0 ms-2 as it started from the rest

a = 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 ).

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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.

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Here's what a star student thought of this essay

4 star(s)

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.

Did you find this review helpful? Join our team of reviewers and help other students learn

Reviewed by k9markiii 05/03/2012

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