02-Mar-2015: Free Fall Lab (Learning Excel)

Purpose -  In this lab we will determine the value of gravity while using excel to analyze some data.

The sturdy column provides a 1.5 m falling distance. This device will plot points on a film of paper as a metal piece free falls perpendicular to the ground. We will use the data to make a distance versus time graph and a velocity versus time graph.

The film of paper had dots generated by sparks that we measured with a ruler. At the beginning the dots we close to one another. As we measured the dots they became more spread apart. Each dot was 1/60th of a second apart from one another.

We logged our time, distance, delta x, mid-interval time and mid-interval speed onto excel. With excel we are able to use the program to calculate and input the data in a timely manner. In the time column A3 we entered =A2+1/60 and then dragged the corresponding cells to have excel input the numbers for us. For distance the data was from the paper film we measured. Delta x the formula was =(B3-B2). Mid-interval time was =A2+1/120. Mid-interval speed was =C2/(1/60).

Velocity vs Time
Graphing our speed versus time, we highlighted our data from columns D and E. Selecting the XY scatter graph we were able to obtain what is showing on the left. Using excel to graph our data also allowed us to gain our slope by adding a trend-line in the options.

Mid-interval is the point between each of the 1/60th of a second.

Position vs Time
We obtained the position over time graph the same way as above. The difference is we highlighted our data from column A and B.











            You can see that constant acceleration is shown on the velocity over time graph by looking at the trend-line. The line moving in a straight line upward indicates that the speed is constant. When the speed is constant we know that acceleration is zero. The times at which we have acceleration is the moment the metal piece dropped and when it stops. In this scenario it seems we are trying to determine that gravity will ultimately be our acceleration value.
            To gain the value for acceleration is velocity over time. 

            To gain the value for acceleration from our position over time. 

Column A we took the g values from every group and in the red obtain the average of them all. (=average(A2:A11)
Column B was the deviation from the mean.
(=A2-$A$12 the dollar sign locks in the value we want.)
Column C is the deviation squared. (the symbol to square is "^")











       The pattern of all the values were all lower than the actual value of gravity. Same with the average value of gravity compared to the actual. They are lower due to the air resistance from the metal piece free falling or maybe the sparking from each dot gathering may have caused a slight friction force.
      Systematic errors in experimental observations usually come from the measuring instruments. The calibration of the sparks to annotate the dots could be a factor for this experiment. The ploting of our graphs in excel could be involved with these types of errors.
      Random errors in experimental measurements are caused by unknown and unpredictable changes in the experiment. These changes may occur in the measuring instruments or in the environmental conditions. Air drag due to a gust of wind from the air conditioning system could play a role in determining points. A surge of electricity from the equipment being quite old.

       The value of this lab is to proficiently use excel. If some of the student did not quite understand the commands excel provided, this lab fixed that. Allowing us to find gravity and use excel to assist is another highlight to how this program is efficient. By plotting graphs to obtain an equation that gave us slope. The calculation that excel can do for the students is convenient. On top of all the nice features excel can do for us. It is imperative to understand each of the calculations and the meanings of graphs and the errors that may impact data.