# Accleration Due to Gravity in our Very Own IHS ## Recommended Posts October 20, 2010 (Rochester, NY) – Irondequoit High School Students/physicists looked to test the accuracy of their reference tables in a Kinematics and Gravity Lab. For weeks they had been trusting Mr. Fullerton’s, their physic teacher’s, answer for the acceleration due to gravity: 9.81m/s². However today, they used a tape measure, a stop watch, and a large red ball to calculate the acceleration due to gravity themselves.

When interviewing one of the groups of students they took me through their procedure to find the acceleration due to gravity. One student held the ball careful 2 meters above the classroom floor (another student measured the height with a meter stick). “We wanted to make the distance simple so that our calculations didn’t get too messy,” said Phoebus Houston, a senior in Mr. Fullerton’s class. Then another student took the stop watch, counted to three and at three, she pressed start on the stop watch while the partner holding the ball released it. As soon as the ball hit the ground, they stopped the stop watch. “We repeated these steps 3 times, doing three separate trials to get the most accurate answer we could.”

Then, knowing that the initial velocity of any object that is dropped is 0 meters per second, the group used the initial velocity and displacement of the ball (2m), both constants in each trial, and the time recorded in each trial to calculate the acceleration due to gravity for each trial. They plugged these numbers into the kinematic equation, d=Vit + 1/2at after they solved for the variable a (acceleration) first. “Finally, we took these three accelerations, added them together and divided them by three to get 8.34m/s².”

I then asked this group why the physics reference table in their classroom said that acceleration due to gravity was 9.81m/s², but they got 8.34m/s²? “Well in the second and third trials we got the same recorded times, but for the first trial our time was .50 seconds longer than the other two.” This large difference explains one reason why their percent error was 15%. Of course that is the percent error they gave me, so how accurate is that?

They told me later, before I left, that if they could have done anything differently for their procedure, they would have performed more trials.

“We are glad we got as close as we did and can’t wait to launch our catapults next week.” For more news on the catapult project visit our website at www.gingerpost.com.

##### Share on other sites In the physics world at IHS, a new experiment took place in order to figure out the acceleration due to gravity. This experiment requires a ball, tape measure, and a stop watch. To begin this experiment, one must first measure the tape measure to one meter, vertically. Then, while one group member is holding the tape measure one meter up, another group member should drop a ball from the top of the meter. As the ball is dropping, the last group member should time the amount of time it takes for the ball to reach the ground. This requires three trials in order to have adequate data. Once the data is retrieved, the calculations begin.

In order to calculate the acceleration due to gravity, a, a kinematic equation must be used in order to do so. In this case, the equation that will be used is as followed:

d=vit+.5at^2

This equation is solved for by filling out the motion chart:

vi=

vf=

a=

t=

d=

This equation must be used for each trial in order to find the average acceleration due to gravity.

For the first trial, the average acceleration due to gravity is 20.8 m/s^2

For the second trial, the average acceleration due to gravity is 19.5m/s^2

For the third trial, the average acceleration due to gravity is 22.2m/s^2

Therefore, the overall average acceleration due to gravity is 20.8m/s^2

Although result were achieved, they were not very accurate after finding out the perfect error. In order to find the perfect error, you use the following formula:

|measured-accepted value|

-------------------------- x 100

| accepted value |

The percent error for this acceleration due to gravity is 112%. Not very accurate Overall, the experiment and forumlas for finding the acceleration due to gravity were very simple and easy to do. However, they were not as accurate as the actual acceleration due to gravity: 9.81m/s^2

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• 11 months later... Breaking new from Irondequoit High School Mr. Fullertons physics class just confirmed the age old discovery that acceleration due to gravity is 9.81m/s squared. They did this by drooping a dodge ball from a selected height and then finding the mean. From that number they were able to calculate the acceleration due to gravity from the equation d=vit+1/2atsquared which resulted in the answer of 11.4m/s squared. They then calculated there percent of error which resulted to be 16 percent which is actually quite low given that they only used stop watches. It truly is amazing what kids are able to do with such basic tools.

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