Lab #9: Centripetal Force with a Motor

Purpose: To come up with a relationship between the angle that the hanging mass makes with the vertical and the angular speed of the apparatus.

The apparatus:
The motor mounted to the top of a tripod spins a pole with a two-meter stick with a hanging mass at one end. This apparatus is similar to a carnival "swing-merry-go-round".







Procedure:
1. Before turning the motor on we measure everything that will remain constant troughout the experiment: The height of the apparatus(H=2m), the radius where the hanging mass is attatched(R=.98m) and the length of the string for the hanging mass(L=1.645m).

2. We then drew force diagrams and symbolically solved for both the angle and time. (note* the height we will measure is from the ground to the rotating height of the mass denoted by the lowercase "h").

3. After deriving the formulas we used we came together as a class to observe the apparatus spin at different speeds. For each speed we timed ten rotations and divided that by ten to calculate the time for ohe rotaion. Each speed also provided us with a new height "h" that we measured by slowly raising a piece of paper on a ring-stand until the mass barely nipped it, pulled it aside and measured the height. We collected data for each of the six runs we had at increasingly greater speeds.

4. Once the experimental data was collected we went back to our equations and plugged in "h" and calculated our theoretical values of both the angle and time.

5. To compare our actual to our theoretical results we plotted them agains one another and had logger pro insert a line of best fit to show us how accurate our process was.