Physics Demo Number: 082

Approximate Run Time: 10 min

Tension in String Visualized in Conceptual Manner

Demo Description

Measure the tension in a string looped over a pulley and attached to a mass.

 

Scientific Principles

  • Newton's 3rd Law

  • Ropes and Pulleys

Equipment & Set Up

  • Pulleys and stand hardware

  • Masses and strings

  • Tubular precision Newton balance

 

Equipment Location

  • All parts, except set up poles and clamps, are in Kit (082) on [F-3-5].

  • Set up poles and clamps are on [G-1-3]-[G-2-3] and [G-1-4]-[G-2-4].
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2

Instructions

The components are pictured in photo 2.

Note that one should not use more than the 500 gm masses to avoid damaging the( blue and yellow) balance (which is only good to 10 Newtons and which is very expensive to replace).

Photo 1 shows the basic setup with a 500gm mass hanging from each pulley and the tubular balance having its ends tied, respectively, to the other ends of the two pulley strings.

The balance of course reads about 5 Newtons.

One may remove one pulley and mass and tie the string (which went over that pulley to that mass) to the setup pole for amplification of the conceptual principles being contemplated.

One may also( of course ) hold the afore-mentioned string in his/her hand and let the other mass (removed from its pulley) hang vertically below the hand to again observe a 5 Newton reading on the balance.

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Alternate setup:
None

The third photo shows a dedicated pulley (on a dedicated horizontal rod ) residing in a clamp atop one of the big set-up stands.

The rod , pulley, and tubular balance live in kit 082 on [F-3-5] along with the two 1000 gm masses.

Thus one may pull the parts out of the kit and clamp the pole hoizontally in the the big set-up stand next to the lecture room door.

Then the equipment in the state pictured shows the tension in the string to be about 5N.

Holding onto the left segment of the string one may remove the 1000 gm mass on the left, without changing the tension reading.
  
Writeup created by David A. Burba
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