Setup: The image below is the basic setup for the circular motion lab. We start by setting the pointer (red B) all the way in toward the rotating shaft by loosening the screws at its base.
Then unhook the spring and the string weight (if you have already hooked them up) and make adjust the distance the cross bar extends from the rotating shaft until the tip of the bob (red A) is directly over the pointer. Remember to do this every time you adjust the distance or radius of rotation.
And remember to double check that the cross bar didn’t move at various times during the parts of the experiment where radius will remain constant.
Then re-hook the spring and string with the hook weights as pictured and add weight until the tip of the bob and tip of the pointer are in line.
Remove the string and hook weights until the setup looks similar to the picture below.
While carefully holding the base spin the shaft with thumb and index finger adjusting your speed until the tip of the pointer and tip of the bob are again in line. Then while still maintaining the appropriate speed use a smartphone or web-based stopwatch to measure the time for 20 complete rotations.
WEAR SAFERY GOOGLES and make sure everything is secure and clear of the rotating bob.
Keeping the radius from the last part of part 1 we increase the mass of the bob by adding weights to it as shown below. Make certain to turn the slot on the weight outward from the center of rotation to help prevent it from fly off if the nut should come loose.
In the third part we will adjust the frequency by adding different size paper clips in between the spring and the rotating shaft.
Remember every time you change something you want to verify that the radius of the pointer and cross arm are still accurate and haven’t moved and to re-measure the weight by re-attaching the string and hook weight.