Centripetal forces at play

This lab partially fulfills competency 6 of the FlexTech physics course. Pre-requisites are completion of Algebra 1 and Geometry, and physics competencies 1, 2, 3, and 4.


At some point, you've probably experienced being spun around on some contraption like the one pictured. As you speed up, it may seem like there is a force trying to throw you off ("centrifugal force"). Actually, Newton's First Law says that you should travel in a straight line, unless acted upon by an external force. The force you feel is the merry-go-round pulling you away from that straight line path, and we call that centripetal force. So, as you speed up, the force increases. This raises other questions. Does your mass affect the force? How about the size of the merry-go-round?

What provides the centripetal force when a car goes around a corner? Can you predict how much force is needed to keep a car from leaving the road?

To understand what determines centripetal force, I have created a virtual lab. A rotor arm spins with some kind of motor driving it, and it can be adjusted in length and rotation speed. A mass is attached near the end of the arm, and the pull of the arm on the mass can be measured. We can imagine the rotor is spinning horizontally. So in the simulation below, we are looking down from above. Or if you prefer, you can assume this happens in space. Also, assume the hub at the center does not move significantly (it is very massive, or secured to something massive).

Can you gather data, and use it to discover the relationship between force, mass, radius, and the speed of the mass? See the centripetal force lab handout.