Measuring gravitational acceleration in a vacuum

[Skorbee]

I have to measure gravitational acceleration, and calculate my rate of error.
The experiment i came up with is: a thick plastic tube, with no air inside,
on the top side some sort of release mechanism, then have two motion detctors, 1M apart from each other, hooked up to a stopwatch to measure the time taken for an object to fall that one meter.
what do you guys think of this experiment?
anything that i need to improve on this experiment?

 

[RTW69]

This experiment will work however removing the air from the column is probably not necessary unless you are dropping a feather. There are lots of ways to measure "g" ,the trick is accurately measuring the time for the object to drop. Google "measuring acceleration due to gravity" will give you lots of ideas including using pendulums and super balls.

 

[Skorbee]

Thanks,
Have you got any good directions as to motion detectors?
should I just pull apart one of those motion detectors for garage lights?
Regards, Steven

 

[RTW69]

You might try this. You can probably get this article at a collage library or interlibrary loan. RTW

A stopwatch-based photogate timer
The Physics Teacher -- October 2000 -- Volume 38, Issue 7, pp. 405-407
Issue Date: October 2000
This paper describes the construction of an inexpensive photogate timer that uses a flashlight-infrared phototransistor photogate and a simple electronic circuit that triggers an electronic stopwatch. This photogate timer uses readily available parts and is relatively easy to construct.