Measuring the acceleration due to gravity in the lab.
02/05/07 Tausif Ahmed 10S
Measuring the acceleration due to gravity in the lab
Our aim was to find the acceleration due to gravity in the laboratory.
The distance between the ceiling and the floor (h) was measured. A rubber was then dropped from the ceiling and the time taken for it to hit the ground was recorded.
Average Time = Sum of all times
Number of Times
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= 0.59 sec (to 2 dp)
H = height of the drop
T = time taken
Acceleration due to gravity = 2H
= 14.88 m/s2 (to 2 dp)
The results circled in the table are anomalous. There was a wide range of results, from 0.4 to 0.71. This spread of results indicates that the data may be inaccurate. Although the experiment was repeated nine times, different results were found at nearly every attempt. This could be due to the timing methods used. A stop clock held by a person was used to measure the time the rubber took to hit the ground. As a human’s reaction times are not perfect, the button could have been pressed long after the rubber had touched the ground. Also, the timekeeper could have pressed the button too early; at the time he expected the rubber to fall in order to try and get a more accurate time. As the area used was not a vacuum, air resistance would have affected the results. The shape of the rubber dropped was a pyramid, so air resistance would be different dependant on the side upon which it was dropped. These reasons explain why some of the results were anomalous.
I do not believe that the procedure was accurate enough to measure the acceleration due to gravity in the lab. The timing apparatus was too imprecise and the air resistance due to the lack of a vacuum meant that the data was not as exact as was needed.
A more suitable set of timing equipment would have been to replace the stop clock with a light-gate and data-logger. A light gate would be positioned at the top of the drop, with one at the bottom. The computer would then calculate the time taken much more accurately. The air resistance could not be helped, as a vacuum would be highly impractical and unnecessary for our purposes. However, if it were possible, the experiment should have been performed in a complete vacuum. If a perfectly spherical object were used then the air resistance wouldn’t be different no matter how it was dropped.
The experiment should be repeated in exactly the same fashion as before, but with the changes outlined above implemented. This would give more accurate results. It should then be repeated in the same way as this, but with a denser object of the same dimensions. This would show that the acceleration was due to gravity and not the mass of the object. One more experiment should be undertaken with the same stipulations but an increased dropping height. This would show that the acceleration is the same no matter how high the object is dropped from.