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This is a two part demo though just one of the parts may be chosen. A mass is suspended from a string connected to a string-suspended spring scale. The string suspending the scale is then run over a pulley and attached to another spring scale which is held by the instructor. The registered tension is the same in both cases. Two spring scales are used to show that the tension within a string attached to a hanging mass is the same on both sided of a pulley, then shown as a static free-body example with one spring scale.
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 1. List steps for setup then procedure.
 1. ...		 Part A:
 1. Fasten the rod/clamp setup to the lecture bench.
 1. Hang one spring scale with a string from the cantilever of the rod/clamp setup (see photos).
 1. From the suspended spring scale, hang the 5 kg mass with a string.
 1. The force reading on the spring scale is the tension in the string.

Part B:
 1. Building on part A, switch the top string suspended the scale with the longer one and run this over the pulley.
 1. Attach the second spring scale to the long string.
 1. Hold on to the bottom hook so that the string remains taught - the readings on the two scales should be the roughly the same (ignoring friction and the mass of the pulley).
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Discuss the physics behind the demonstration, explaining some of the various steps of the demonstration when appropriate. When a string is taught, there is force along the string.

[:PiraScheme#Mechanics: Table of Mechanics Demonstration]

[:MEEquipmentList: List of Mechanics Equipment & Supplies]

[:Demonstrations:Lecture Demonstrations]

Tension in a String, 1J30.20

Topic and Concept:

Location:

Abstract:

Two spring scales are used to show that the tension within a string attached to a hanging mass is the same on both sided of a pulley, then shown as a static free-body example with one spring scale.

Equipment

Location

ID Number

Newton Scale

ME, Bay B2, Shelf #1

String

ME, Bay B1, Shelf #2

5 kg Weight

ME, Bay B1, Shelf #2

Important Setup Notes:

  • N/A

Setup and Procedure:

Part A:

  1. Fasten the rod/clamp setup to the lecture bench.
  2. Hang one spring scale with a string from the cantilever of the rod/clamp setup (see photos).
  3. From the suspended spring scale, hang the 5 kg mass with a string.
  4. The force reading on the spring scale is the tension in the string.

Part B:

  1. Building on part A, switch the top string suspended the scale with the longer one and run this over the pulley.
  2. Attach the second spring scale to the long string.
  3. Hold on to the bottom hook so that the string remains taught - the readings on the two scales should be the roughly the same (ignoring friction and the mass of the pulley).

Cautions, Warnings, or Safety Concerns:

  • N/A

Discussion:

When a string is taught, there is force along the string.

attachment:TwoScaleSetup02-250.jpg

attachment:Scale01-250.jpg

attachment:WeightStringsScale02-250.jpg

Videos:

References:

[:Instructional:Home]

fw: Tension_in_a_String (last edited 2013-07-12 18:17:34 by localhost)