Lab 2: Motion and Gravity

Lab 2: Motion and Gravity


– Operator

 – Theorist

 – Recorder



Theory and Procedure

Lab Objective: TO study motion in one dimension and determine g, the acceleration due to gravity.

Due to the parking garage being unavailable until a later time, we started the lab at step 3, and our report will follow that procedure.

We began by dropping a ball under the sonic range finder, looking to calculate a number sufficiently close to the expected value of gravity: 9.81. We experienced several difficulties in measuring this value. Many, if most, of our graphs were extremely steep and yielded very high values of gravity (200+), we knew that this could not be right and so tried several more times, using balls of various size. Eventually, we calculated a value that was sufficiently close to g, by including in the graph a small curve that occurred before the linear motion. This small curve is included in the graph below.

This is the Graph for Part 3 of the Lab, with it, we calculated a value for g equal to 10.84 m/s^2. The error in this result is %10.5 error.

Gravity was calculated by following this equation: g= (2y)/ (t)^2

After this sonic range finder work, we travelled to the parking garage and dropped 6 golf balls off the top as an alternative method to calculate a value for g. The garage was approximately 11.2 meters tall, and we timed the descent of 6 golf balls as they were dropped off the edge. There was particular difficulty in coordinating the drop time with the time that the recorder began his stopwatch, and so some values were distorted, and clearly off. We choose to negate these values, because they were clearly errors.


The equation for gravity as derived by Mohammad was g=(2y)/(t)^2

Data recorded during the parking garage experiment was

Time of Descent in seconds Gravity Calculated
1.54 9.445
1.62 8.535
1.52 9.695
1.32 12.855
2.13 (negated for error)
1.53 9.568


The table shows that the normal result was very close to the expected value. We negated the Descent values of 1.32 s and 2.13 s when we calculated the average value for gravity which was: 10.016.

This means that we have two values of gravity – one from the parking garage experiment and one from the sonic range finder experiment. We compared these results against the expected value of gravity and calculated a percent error.

Experiment Gravity Value Percent Error
Sonic Range Finder 10.84 10.5%
Parking Garage Experiment 10.016 (Avg) 2.1%


This clearly and distinctly shows that the Parking Garage Experiment was a better experiment to calculate the value of gravity on the surface of the earth. This is an interesting result because we would have guessed that the sonic range finder experiment would perform better. This is because we imagined there would be all sorts of errors outside (wind, coordination problems between dropper and timer etc..) To find that the Parking Garage Experiment performed more accurately than the sonic range finder was a curious result.


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