Force & Motion: Newton's Third Law
Determine the relationship between the forces that are exerted on two Force Sensors during a "tug-of-war."
Students measure the forces applied and easily observe the equal and opposite forces in a static tug-of-war. Students see that even though the force changes substantially, there is no net motion as long as the forces are in balance.
Students explore 3 scenarios: pulling against each other, pulling against a force sensor attached to a fixed object, and pulling a larger mass.
Lab Summary
In this exploration, students will use two Force Sensors to investigate Newton's third law of motion (Newton's Third Law).
Specifically, students will use Force Sensors to measure the forces involved in a tug-of-war. They will compare the plots of force versus time to determine how the two forces are related to one another; that is, the forces are of equal magnitude, but opposite direction.
Theory
If Object A exerts a force on Object B, then Object B will exert a force on Object A that is equal in magnitude and opposite in direction. For two objects attached by a cord, the forces will always be equal and opposite regardless of which one does the pulling.
Downloads
- Computer-based lab (PDF, 956 KB) (953 KB, .pdf)
(student versions)
- Xplorer GLX-based lab (PDF, 232 KB) (228 KB, .pdf)
(student versions)
Method
Use a pair of Force Sensors to measure the forces during a tug-of-war between the two sensors.
Here's What You Need
U.S. Educator prices shown.
Required for computer-based lab: (See lab download for Xplorer GLX-based lab requirements, which may differ)
Probeware
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
Large Rod Base (ME-8735) - $89
A sturdy, general-purpose base can support one or two rods, and is ideal for experiment setups that require extra stability.
Mass and Hanger Set (ME-8979) - $79
Polycarbonate mass hangers with steel posts and "holed' masses that will not fall off. 4 hangers and 27 weights ranging from 1/2 g to 100 g.
Other Materials
- C-clamp
Lab Manual
The computer-based activity is included in Explorations in Physics (PS-2810). The Xplorer GLX-based lab is included in Physics with the Xplorer GLX (PS-2826). Both manuals are complete with Teacher Information pages, student instructions and handouts, and sample data.
For your convenience, we offer bundles which provide the probeware for the
activities in the manual. For more, please see:
Computer-based
Physics Lab Manual and Bundles
Xplorer
GLX-based Physics Lab Manual and Bundles
