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The aim of this experiment is to prove that a falling body has a constant force of gravity on it, no matter what the distance or time taken for the object to fall. The value of gravity or "g" will be determined.

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The aim of this experiment is to prove that a falling body has a constant force of gravity on it, no matter what the distance or time taken for the object to fall. The value of gravity or "g" will be determined.


The most simple example of linear motion is a body falling to Earth. When the body is dropped from a height we know that the object will always fall directly towards the centre of the Earth. This though will not happen if a feather is dropped as due to its shape and the forces of drag, upthrust and various others act upon it with greater effect. So providing these forces in our experiments and calculations are negligible by using suitable materials it is fair to say an object falls towards the Earths centre.


When the plastercine passes through gate A the computer will immediately start the clock.

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The range of results will be from 0.3m to 0.6m. This is because at a smaller distance the computer is unable to register the speeds fast enough, and at a greater distance the light gates do not connect with the computer. By taking 5cm intervals enough results can be taken to plot a graph. 
In order for my results to be reliable I shall take three readings for each distance. An average can the be taken and error reduced as anomolous results would be illiminated. 
As the computer only displays the velocities the most suitable equation of motion to determine "g" would be V² = u² + 2as or V² = u² + 2gs. This equation can be re-aranged to prove "g" is constant by making gravity the subject.

V² = u² + 2gs

V² - u² = 2gs

V² - u² = g


<ALIGN=LEFTV = final velocity 
u = initial velocity 
s = distance between gates


Using the equation would need an average gravity of each reading.

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Using the line of best fit it can be seen that there is an anomolous result when 2s is equal to 1.0m, which is a distance to fall of 0.5m. This meant that the line of best fit has to be brought down to a lower gradient. So the true gradient should be a little steaper. This would increase the acceleration due to gravity. This could be proved by retaking the readings at this point and calculating a new average.

To further this investigation and prove totally that gravity is a constant force a second experiment could be carried out. Of the several available to measure g, it would be possible to select one which does not rely on linear motion but simple harmonic motion instead. By setting up a simple pendulum it is possible to calculate a value of g by measuring the average time for a single pendulum oscillation. If the length of the pendulum is known, it is possible to plot graphs and get a value for g.

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