1J30.20 Tension in a String

Hanging the weight from a single string over a pulley demonstrates that the pulley doesn’t affect tension in the string. Hanging the weight from two strings at 45-degree angles demonstrates that opposing forces increases the tension in each string. Hanging the weight from a string looped over a pulley demonstrates that the tension in the string on one side of a pulley is the same as the tension on the other side.

A small metal bucket hangs straight down from a bright magenta string. The string passes over a pulley above the bucket, and runs down and to the left to a to a dial-style spring scale, which is held at a sharp angle by a hand. The indicator needle marks 14 N.

A small metal bucket hangs in mid-air, suspended by a two strings. Each string is fastened to the bottom of a spring scale which hangs above the bucket. One spring scale hangs above and to the left of the bucket, and the other above and to the right. Each spring scale hangs from a string fastened to the top of the scale. The other end of this top string is fastened to a post above the scale. Each assembly of string, spring scale, and string forms a line inclined at roughly 45 degrees from the post to the bucket. In this photo, the dial of the leftmost scale reads about 8.5 N. The rightmost scale reads about 7.8 N.

A bucket hangs from a spring scale. The spring scale is hanging from a string that passes over a pulley and straight back down to the top of a second spring scale. The second spring scale is separately fastened to the bucket beneath it, so that the bucket and two scales all hang in a straight line down. Each spring scale reads the same value, about 6.5 N.

Location: C2-5 (bucket),  HI (scale)