When a pendulum is lifted, it is given GPE; this is then released as kinetic energy when it is let go. However instead of stopping when the pendulum reaches the bottom of its arc, it continues to move. This is because the piece of string stops it from moving any further towards Earth; therefore it has gravitational energy left over which it can convert to kinetic energy. It then continues to rise in the opposite direction, until it reaches the point where it has the same GPE as at the beginning i.e.) the same height. It then begins to fall once more.
Diagram
Apparatus
Pendulum and length of string, Clamp-stand and boss, Stop-watch, Metre Rule
Method
The apparatus was set up as in the diagram and the length of the string was measured with the ruler. The string was measured from the point where it would pivot when swung to the centre of mass of the pendulum. The pendulum was then dropped from an angle as a stopwatch was started. The pendulum swings were counted, and after ten oscillations (complete movement of the pendulum to back where it started) the stopwatch was stopped and the time noted. This was then repeated twice, the angle did not have to be kept constant but a smaller angle gave more accurate results. The experiment was then repeated for nine different heights at approximately regular intervals.
Fair Test
The non-key factors mentioned in the hypothesis must remain constant during the experiment in order to provide a fair test. Therefore the same pendulum and piece of string were used throughout the experiment. The clamp-stand was kept at the same height, and the pendulum was given a large space to swing in, to ensure nothing that could affect the time of the oscillation came into contact with it.
Safety
The experiment was generally very safe, the pendulums were not swung from great heights for scientific reasons, but if they were, care should have been taken not to hit anyone, as the pendulum weights were heavy.
Results
This is a table of the raw data obtained from the experiment entered into a spreadsheet. The following columns were added to manipulate the data into a form I could use.
The following scatter graph is a graph of distance between pivot and centre of mass against time taken for one oscillation.
The line of best fit has a very slight curve. The graph below however is a graph of distance against time squared, this is a straight line.
Evaluation
This experiment can be considered very successful. The results taken were very accurate and plotted a straight line as per my hypothesis.
