Periodic & Circular Motion: Centripetal Force
Develop an understanding of the relationship between centripetal force and its factors: circular speed, mass and radius.
Students discover that circular speed decreases as the mass is increased (holding radius and centripetal force constant).
As student swings the mass in a circle, the force is recorded by the force sensor, and this data can be used to determine the period. Students will use the period and radius to calculate circular speed.
Students discover that the circular speed increases as the radius of the circle increases (holding mass and centripetal force constant).
Lab Summary
In this 3-part activity, students will explore the relationship of centripetal force, circular speed, mass and radius.
In Part A, the radius and mass are held constant, and the circular speed is changed.
In Part B, the radius and force are held constant, and mass is changed.
In Part C, the mass and force are constant, and the radius is changed.
Theory
Objects moving in a circular motion are acted upon by a centripetal force toward the center of the circle. This force is determined directly by the object's mass and the square of its velocity and inversely by the radius. Holding any two constant while varying the third and measuring the force elucidates these relationships.
Downloads
- Xplorer GLX-based lab, Part A (PDF, 912 KB) (910 KB, .pdf)
(student versions)
- Xplorer GLX-based lab, Part B (PDF, 464 KB) (460 KB, .pdf) (optional)
Downloads description
- Xplorer GLX-based lab, Part C (PDF, 1 MB) (1.02 MB, .pdf)
Method
Students will swing a mass on a string in a circular motion while the string is attached to a force sensor. Students will calculate the circular speed using the period and radius. The period is determined from the graph of force vs. time, as students can easily count the number of revolutions using this graph. In each of the 3 parts of this experiment, students will hold two of the remaining 3 factors (centripetal force, mass, and radius) constant.
Here's What You Need
U.S. Educator prices shown.
Probeware
750 Interface, USB (CI-7650) - $679
The 750 Interface allows students to measure force, temperature, pressure, angular velocity, acceleration, current, and magnetic field with a built-in function generator and oscilloscope mode.
PASPORT Force Sensor (PS-2104) - $110
Designed to measure both pulling and pushing forces. Uses range from collisions to tug-of-war. For use with PASPORT Interfaces.
Xplorer GLX (PS-2002) - $349
The Xplorer GLX is a data collection, graphing, and analysis tool designed for science students and educators.
Other Products
Discover Centripetal Force Kit (ME-9837) - $39
The kit allows students to feel the change in centripetal force as key variables are manipulated.
Universal Table Clamp (ME-9376B) - $49
Attach to tables, shelves, or ring stands. Also use it as a versatile rod stand.
Other Materials
- Balance
- Metric Ruler
- Marking Pen
Lab Manual
This activity is included in Physics with the Xplorer GLX (PS-2826), complete with Teacher Information pages, student instructions and handouts, and sample data for a total of 35 probeware-based labs. For your convenience, we offer bundles which provide the probeware necessary for the activities in the manual. For more information on these resources and bundles, click here.
