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How to Solve Pulley Force

A pulley system is a system consisting of a wheel or multiple wheels on the axle with grooves in the middle. A rope, cable or chain wraps around the groove, thus creating the tension required to serve as a hoisting system. The tension is effectively the pulley force acting in the opposite direction of the weight. Tension is measured in units of pounds (lbs), just as the weight. A pulley system can be a single rope with a single wheel, or it can have multiple wheels and multiple ropes.

Instructions

- 1
  Determine the weight, or "W," of the object the pulley is attempting to lift.
- 2
  Find the number of times the pulley rope wraps around the pulleys, or "N." For example, a typical pulley system has two wheels, one at the bottom near the weight and one at the top near the hoisting anchor. N represents the number of times the rope cycles around each wheel. See Reference 1 for a visual reference.
- 3
  Calculate the tension on the pulley rope using the following formulas:
  
  T = W/N, if the pulling force is downward. The pulling force refers to the lifting direction. See Reference 1 for a visual reference.
  
  T = W/(N+1), if the pulling force is upward.
  
  Again, see Reference 1 for a visual reference. As an example, W is 200 lbs, N is 3 and the pulling force is downward:
  
  T = 200/3 = 66.6 1bs

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