Science Buddies: "Ask an Expert"

Hi I'm doing this project: https://www.sciencebuddies.org/science- ... #procedure
and i need to be able to calculate centripetal force. I know that in order to do so I need to measure the radius of path that the chamber travels and I'm wondering how I should do that.

Thanks!

Hello tmorelli,

The project procedure instructs you to make a “centripetal force generator cup” used to hold the Jello/marble cups. Next, you “twirl the cup above your head...making as wide a circle as you feel comfortable with” . With this procedure, the radius of the cup’s path is somewhat uncertain and may vary depending on how you twirl the cup.

You might try having someone hold a piece of poster board above your head. With a pen in your hand make your twirling motion so that you draw a circle on the poster board. Then measure the radius of the circle.

Some useful information on calculating centripetal force can be found here:

http://hyperphysics.phy-astr.gsu.edu/hbase/cf.html

I hope this helps. Please post again if you have more questions.

A. Norman

Thank you so much that's a great idea! Do you think if i just spin the cup around my finger I could assume that the radius is the distance between the top of the string handle and the bottom of the cup?

Thanks again,

Tess

Hi Tess,

You’re welcome.

Yes, if you could spin the cup around your finger, the radius would be the distance between the top of the string and the bottom of the cup.

I haven’t tried this experiment but the project procedure indicates that you need to spin the cup fairly hard to get the marble to move within the Jello. So you may not be able to spin the cup around your finger with enough force (or you might injure your finger). Maybe you could try spinning the cup around a dowel rod (say ½ inch diameter).

I hope this helps. Please post again if you have more questions.

A. Norman

Great idea! Thanks again for all of your help