Physics: Why did my object not meet avg. acceleration due to gravity?

if air resistance doesn't count either i would suggest talking about the angle of the book drop. i dnt know what sort of sensor u used but i would presume something like a lightgate if that is the case then the alignment of the book with the lightgate and the angle at which the book fell are very relevant; this is because u use the length of the book as a reference for calculating initial and final velocity or to calculate initial velocity and then use the equation s=ut+1/2 At^2 but any difference in drop angle would cause a change in the crossection of the book crossing the light beam of the lightgate.

(i agree with oldprof though, it is nonscientific to assume perfect equipment)

You really have a terrible lab book. All those sources of error you disallow should and would actually be considered if this were a grown up experiment. Thinking that "the computer took care of everything" is the height of naivete'. Have you not heard of garbage in-garbage out? When you've been in the business as long as I have, you will come to know that the computer, computer operator error, or both are major error sources in experimental results.

OK, discounting the poor lab book, here are just a few of your issues:

First, that 9.8 m/s^2 is just an average value, not site specific. If you're doing the experiment well above mean sea level, you might very well get a lower value and be correct. Remember, g = GM/r^2 and r is the distance between those books and Earth's center.

Second, that 9.8 m/s^2 is the average value when the drop is in a vacuum. Unless you dropped those books in a sealed-off vacuum chamber, it does not apply. There will be air resistance and that will give you an acceleration a = g (1 - D/W) where D is the drag, W is the weight, and a < g is the actual acceleration in air when there is drag D > 0.

Average acceleration A = (V - U)/T; so you might be giving those books a jerk and initial speed U <> 0 rather than U = 0, which I presume you assumed when doing the calculations.

Weight as in W = mg is mass m occasions a g worth that has the units m/sec^2, that are the models for acceleration. So we call g the acceleration due to gravity. But, and it is a large but, it is not consistent as you recommend. G = GM/R^2 actually; where G is a true consistent, M is the mass source of the gravity field, and R is the center to middle distance between something mass is being weighed m and the source mass M. If r is Earth's radius and h is the peak of m above ground, then R = r + h. As you'll find if h gets larger and the gap above ground will get bigger, R also will get greater. Because of this g gets smaller considering M is Earth's mass and fixed. And there you're, g varies "relying on its distance from the bottom." Your confusion comes from poorly written textbooks who claim gravity acceleration g is steady. It is not. G is steady just for a fixed position R and mass M...Or else g varies. Once I use g = 9.81 m/sec^2 in my answers, which is a normal quantity we see in textbooks, I just about invariably specify "near Earth's surface," which fixes R and M for a given question. Wherein case, g is correctly 9.81 m/sec^2, however just for those conditions. If you have been to crunch g = GM/R^2 for the Moon mass M and radius R, you'd find that g is set 1/6 that of Earth's g. So if you're a little chubby on earth, you could weigh in at 1/6 your Earth weight on the Moon.

How about air resistance?

The air resistance could be reduced by decreasing the distance between the release height and the sensors, as the force of air resistance is related to the speed of the object, therefore dropping it through less height would decrease the average velocity, therefore decreasing the average air resistance force.

The Old Prof nailed it. Here is an example of what he is talking about from one of the premier and respected advanced research facilities in the world, the LHC at CERN. If those people screw-up, some high school physics class is not immune. Bad data from faulty equipment? Nah!!! Never happen!

Neutrinos and FTL

The final nail in the coffin may have been dealt to the idea that neutrino particles can travel faster than light.

The same lab that first reported the shocking results last September, which could have upended much of modern physics, has now reported that the subatomic particles called neutrinos "respect the cosmic speed limit."

Physicist Sergio Bertolucci, research director at Switzerland's CERN physics lab, presented the results today (June 8) at the 25th International Conference on Neutrino Physics and Astrophysics in Kyoto, Japan.

"Although this result isn't as exciting as some would have liked, it is what we all expected deep down," Bertolucci said in a statement.

The new findings come from four experiments that study streams of neutrinos sent from CERN in Geneva to the INFN Gran Sasso National Laboratory in Italy. All four, including the experiment behind the first faster-than-light findings, called OPERA, found that this time around, the nearly massless neutrinos traveled quickly, but not that quickly. [10 Implications of Faster-Than-Light Neutrinos]

Last year, OPERA measured that neutrinos were making the 454-mile (730-kilometer) underground trip between the two labs more speedily than light, arriving there 60 nanoseconds earlier than a beam of light would.

At the time, the physicists were stunned because such a result seemed to break Einstein's prediction that nothing could travel faster than light. This idea is at the heart of his theory of special relativity, on which much of our modern technology and scientific understanding is based.

The OPERA researchers weren't sure what could explain their anomalous results, having checked and rechecked their work, so they released their findings to the larger community of physicists in hopes that experts around the world could help them figure it out.

"The story captured the public imagination, and has given people the opportunity to see the scientific method in action — an unexpected result was put up for scrutiny, thoroughly investigated and resolved in part thanks to collaboration between normally competing experiments," Bertolucci said. "That's how science moves forward."

Labs around the world, including the other experiments at Gran Sasso — called Borexino, ICARUS and LVD — as well as the MINOS experiment in Illinois and the T2K project in Japan, tried to recreate the OPERA findings. None were able to do so: Every time, neutrinos appeared to obey the speed limit of light.

Now, the OPERA scientists think their original measurement can be written off as owing to a faulty element of the experiment’s fiber-optic timing system.