Lab Session 8 - UARM

Objective:

Determine the acceleration of an object falling along an inclined plane by different methods.

Table with the relation between distance and time:

Conclusion:

The three graphs went like it said in the background information, as the results all of them are ascending through the graph.

The first graph that is comparing the distance travelled of the marble and the time that the marble last to cover the distance, we can see that both values are directly proportional and that is why it has that shape. The shape of the graph seems reasonable as when the distance is bigger, the marble will last more time to reach the point.

As seemed, the graph that compares the distance and the squared time is very similar to the first one, as it compares the same variables (distance and time), but this time the graph has more gradient as the time is square. And as it's squared, the values are bigger. We could also say that both values of the second graph present also directly proportional values as when the distance increases, the time squared increases too.

Thirdly, the last table present a comparison between the velocity of the marble and the time. This graph is like the other previous graphs, when talking about it shape (ascending, like the other two) and the values (directly proportional, like the other two, as when velocity increases, the time increases too). We could say that the three graphs went how it was supposed so the experiment was well done.

Finally, it is important to say that the acceleration should be the same always as it shouldn't change, but it changes in some values in the data because of some errors that will be explained in the evaluation of the method.

Evaluation of the method:

The first error that we founded is that when we were doing the third trial in the 1 meter and a half distance we slightly push the marble when we drop it. This caused that the marble went faster than in the other 2 trials and affect directly in the average. This is an example of a human error that could affect the final result. To solve this error we must try to be more careful and in the case that this incident is repeated we must have to do it again.

The second error that we founded was that when we stopped the chronometer in each trial we did it when the marble was few millimetres further from the mark. So when the chronometer stops, the marble had cover more distance that it should. The distance was not exactly as we planned and that could affect the final result. This is a systematic error as it arise from a problem in the experimental setup that results in the measured values always deviating from the “true” value in the same direction. This is a derivation of the parallax error as it is caused mainly by seeing the object at an oblique angle so we think that a way to solve this error is to stop with the hand the marble exactly in the mark.

The third error that we founded was that, as the experiment was long and we were always touching the aluminium rails, the aluminium rails had a different slant. Before starting with a new distance we put correctly the aluminium rails but during the trials inadvertently we could have moved them a little. This is a very important factor because a slightly difference of slant can affect the final result as it obtains more or less velocity. This is an example of random error as it is caused by unpredictable changes in the equipment or conditions of the experiment. It can be solved by fixing the aluminium rails to the wood pieces with adhesive tape to avoid it movement.

Photos of the procedure:

Materials:

Aluminium rails

Marble

Ruler

Wood pieces

Process:

1)Put the rail over the wood pieces with some angle.

2) Make five marks regularly spaced on the rail.

3) Measure with the meter the distances from the start to the marks.

 4) Drop the marbles from the start and measure the time they last to the marks. Repeat the measurements at least three times from the start.