Sorry if I fill any of this out incorrectly, this is my first post. 1. The problem statement, all variables and given/known data Basically, we are told to calculate gravity with the use of a pendulum. Now, this part I understand, alter the length, record the period at each length, calculate averages and substitute these averages into the formula, T = 2pi sqrt (L/g) 2. Relevant equations As stated above. 3. The attempt at a solution I have obtained my average for gravity, which is 9.53m/s^2. But I need some clarification on a few minor things. In my scientific discussion, I have said that: -human reaction time -Friction -Air resistance -Weight Distribution (of the mass on the end of the pendulum) All play a part in the result for gravity not being 9.8, however there are a few things that I am tempted to include, but not too sure if they are correct. 1. The very, very, very small impact that the gravitation force between the metal mass on the end of the pendulum and the metal retort stand used to hold the pendulum has. I.e, this small gravitation field is slightly altering the course of the pendulum and as such slightly altering the period time. 2. The elasticity of the string (fishing line) used on the pendulum. Wouldn't there be a very small amount of elasticity which would be altering the length of the string throughout the course of its period? Any help would be really appreciated.