Acceleration On A Scale
To illustrate forces in an accelerating system.
Mass hanging from spring in frame hanging from spring scale, as photographed.
Ask your students what will happen, and why, before doing the experiment.
A rigid frame hangs from a spring scale as photographed. In the frame, a mass is pulled down and attached to a hook at the bottom of the frame by a short thread loop. (Ask your students how this mass hangs from a spring. The affects the weight shown by the spring scale.) In this position the spring scale reads about 8 Newtons. Q: When the string is burned, releasing the mass, will the reading on the spring scale immediately after the string breaks (a) increase, (b) decrease, or (c) stay the same? A: It will increase.
Richard M. Sutton, Demonstration Experiments in Physics, Demonstration M-114. Acceleration on a Balance. C. Frank Griffin and Peter N. Henriksen, Physics challenges, TPT 18, 135-136 (1980).