Acceleration of Gravity

Acceleration of Gravity

The purpose of this lab was to determine the acceleration of gravity for a freely falling object.  In our previous lab we played around with the computer using it as a data collector so our experience this second time around was a lot more rewarding. 

The equipment used were the same as last lab: Windows based computer, Lab Pro interface, Logger Pro software, motion detector, rubber ball, and a wire basket.

We began by connecting the lab pro to the computer  and the DIG/SONIC2 port to the lab pro.  We loaded the logger pro software to the computer this is found within the Physics Apps Folder and Opened the mechanics folder. Once inside the folder we open the graphlab file which is used to set up the computer for collecting data. Once we opened our folder and got a blank r vs t graph we place the motion detector on the floor and the basket over it to protect it.  We checked that it was working properly by testing the data colletion with a piece of carboard.  Everything seem to be working fine so we began to Collect data.  We tossed the ball stright up and watched the computer collect data.

 

 After adjusting our time on the x axis to 4 seconds and a couple of tries a nice parabolic curve appeared on our position vs time graph.  The graph showed a steady line that was probably when we were holding the ball.  Then it goes up with the toss and it heads back down pass the initial stating point. We then choose the Analyze/Curve Fit from the menu and put     a t^2+b t+ c (Quadratic equation form).  We selected the points from 1s to 2s the selected try fit.  A curve almost identical to ours appeared . After pressing ok it gave us a box with the values of a, b and c.  Based on Unit Analysis 2A gives us our acceleration Gexp, we toke this value and pluged it in to the formula for calculating error percentage.
     










percent error= measured -actual / actual  x100%



 Then we double clicked on the y-axis and selected velocity and deselected position.  The velocity graph appeared.  The graph shows a velocity thats moving in a positive direction and slowing down that was when the ball was tossed up, then it hits 0 at the peak of the curve before turning back in a negative dirrection and speeding up in velocity this was when the ball ran our of juice and begun to head back down towards the ground.  It continued to go pass the starting point thats because the ball was released from a meter above ground.  In the same manner as the r vs t graph we measured the % error.  We did this 5 times got and average value rand the percent error calculation. 
On our black boards we sketched up all three graphs. r vs t  a vs t  and a motion graph.  In the motion graph which is the graph in the bottom you can see that the motion is moving in a positive direction and then it turns around and goes in a negative direction.  This should help explain acceleration having a positive and then a negative slop. The slop is positive decreasing and the it turns around negative increasing.