Mechanics: Tug of War

PIRA Class: 1H10.10*

Purpose:
To demonstrate the equal forces (of Newton's 3rd Law) acting on two opposing bodies.

Description:
Students observe equal readings on spring scales while 'playing' tug of war.

1. Attach the spring scales to the ends of a rope.

2. Have two students pull on spring scales and simultaneous read aloud the scale readings.

3. Variations: Have one student actively pull and the other simply hold on. Have the students do the experiment while moving (both moving the same direction). Attach one scale to an inert object (wall or door).

4. For a smaller, single student demonstration the scales can be linked directly to each other or using a short string.

NOTE: Spring scales are difficult to calibrate perfectly. Try the experiment in advance working to shift each scale dial by hand to calibrate.

Equipment:
Two large spring scales, sturdy rope

Location:
Shelves 123 & 124