The aim of this investigation is to investigate the effect of adding varying weights to the end of a wooden ruler at different ruler lengths.

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Physics Coursework: Ruler Investigation.

Introduction/Plan:

        The aim of this investigation is to investigate the effect of adding varying weights to the end of a wooden ruler at different ruler lengths.

        I predict that as the weight increases on the ruler the more it will sag and the more it will sag each time, demonstrated by this rough graph:

There should be a strong positive correlation between the sag and the force

I predict this because of the rule of compression and tension; as more force is exerted vertically onto the end of a ruler, the top face becomes tense and the bottom face becomes compressed. The explanation of this will be in my conclusion. I also make this prediction using the formula of moments:

Moment of a force (Nm) = force (N) x perpendicular distance from the pivot (m)

This will also be explained in my conclusion.

        (The diagram of my method is shown above next to my predicted graph shape). A wooden metre rule will be clamped onto a table using a G – clamp with a certain distance sticking out from the table. Another metre rule will be clamped with a retort stand at right angles to the floor so to measure the sag of the other ruler. The weights will be added to the ruler at three different lengths they will be added in one hundred gram amounts for each length (of the ruler) to the end of the ruler with some string and sticky tape (100g to 1000g). Before this is done however a reading will be taken from the vertically mounted ruler to find out how many cm will need to be taken away from the results to give the correct sag of the ruler. As the weights are added, care will be taken to make sure that the weights are not added and the ruler then dropped suddenly so as to reduce the risk of the ruler splintering.

Apparatus Used:

  • Wooden metre rule
  • G – Clamp
  • A second ruler with which the sag will be measured
  • Weights ranging from 1 to 10 Newton’s, in increments of 1 Newton (therefore 10 of them)
  • String and tape to put around the ruler with which the weights will be tied

Each reading will be taken three times so as to make the results as accurate as possible. An average will then be taken to make the investigation more accurate and to take into account all three results for each point equally. It all will be presented in a table.

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        There are certain factors which affect this investigation, they include: the length, thickness and material of the ruler, the accuracy of the weight of the weights being used, how far along the ruler the weights are situated and any human error involved. To make this investigation a fair test the only variables will be the force exerted on the ruler and the distance along the ruler that force is.  

        All my results will be to one decimal place as well as the averages taken from each set of three results.

A preliminary experiment was carried out initially to ...

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