The New Lab!

Hey everybody!

As discussed in class, the new lab will have you trying to determine the acceleration due to gravity.  We have heard that this should be close to 9.8 m/s/s, but how can we be sure?  Here are some techniques for finding this value.

1.   The dropped object method.

Drop an object from a measured height (d) and record the time (t) for it to fall.  Calculate the acceleration (a) from this.  You can try a large height (such as in the atrium, using a stopwatch), or you can use a small height with a photogate (and shut-off switch) set-up.


2.  The pendulum method.

You know from earlier in the year that the period of a pendulum (T) is given by an equation:

In this equation, T is period/time for one swing (in seconds), L is length (in meters), and g is the acceleration due to gravity.


3.  The ticker-tape method.

This is maybe the most novel method, and it gives you a lot of data.  However, the analysis is probably the longest.  A ticker-tape timer will vibrate 60 times per second (60 Hz is the frequency), which will give 60 dots per second on a piece of "ticker tape."  By measuring the distance between dots and calculating the increasing speeds - details to be discussed in class - you can, in principle, determine the acceleration.

4.  The single photogate method.

In this method, you will release a ball from rests and allow it to fall a measured distance (d).  It will achieve a certain velocity (Vf) at the bottom of the fall - the photogate should give you the final velocity, if used correctly.

So there you have it - 4 methods for finding g.  There are others, of course, but these 4 can be done in our classroom.


Consider these 4 methods and decide which one is most interesting to you.  You will perform the experiment during the next class.

In preparation, start to write-up a tentative outline of how you plan to collect data.  It is ok to leave out the technical details at this point, since you probably don't know how to use the new equipment yet.

In your final lab report, you will have a detailed procedure - something that a total stranger could conceivably follow - and a materials list.  You will have other lab report things as well.